STL源码剖析——STL算法stl_algo.h
前言
在前面的博文中剖析了STL的数值算法、基本算法和set集合算法，本文剖析STL其他的算法，例如排序算法、合并算法、查找算法等等。在剖析的时候，会针对函数给出一些例子说明函数的使用。源码出自SGI STL中的
STL算法剖析
#ifndef __SGI_STL_INTERNAL_ALGO_H
#define __SGI_STL_INTERNAL_ALGO_H
#include //这里包含堆的相关算法
//最大堆的相关算法已经介绍过了，有兴趣详见
//http://blog.csdn.net/chenhanzhun/article/details/39434491
// See concept_checks.h for the concept-checking macros
// __STL_REQUIRES, __STL_CONVERTIBLE, etc.
__STL_BEGIN_NAMESPACE
#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1209
#endif
// __median (an extension, not present in the C++ standard).
//函数功能：取三个元素a，b，c的中间值
//版本一采用默认的operator<操作
template
inline const _Tp& __median(const _Tp& __a, const _Tp& __b, const _Tp& __c) {
__STL_REQUIRES(_Tp, _LessThanComparable);
if (__a < __b)
if (__b < __c)
return __b;//若a
inline const _Tp&
__median(const _Tp& __a, const _Tp& __b, const _Tp& __c, _Compare __comp) {
__STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
if (__comp(__a, __b))
if (__comp(__b, __c))
return __b;
else if (__comp(__a, __c))
return __c;
else
return __a;
else if (__comp(__a, __c))
return __a;
else if (__comp(__b, __c))
return __c;
else
return __b;
}
// for_each. Apply a function to every element of a range.
//功能：Applies function fn to each of the elements in the range [first,last).
//将仿函数f应用于[first,last)区间内的每一个元素上
//注：不能改变[first,last)内元素值
template
_Function for_each(_InputIter __first, _InputIter __last, _Function __f) {
__STL_REQUIRES(_InputIter, _InputIterator);
for ( ; __first != __last; ++__first)
__f(*__first);//调用仿函数f
return __f;
}
//for_each函数举例：
/*
#include // std::cout
#include // std::for_each
#include // std::vector
void myfunction (int i) { // function:
std::cout << ' ' << i;
}
struct myclass { // function object type:
void operator() (int i) {std::cout << ' ' << i;}
} myobject;
int main () {
std::vector myvector;
myvector.push_back(10);
myvector.push_back(20);
myvector.push_back(30);
std::cout << "myvector contains:";
for_each (myvector.begin(), myvector.end(), myfunction);
std::cout << '\n';
// or:
std::cout << "myvector contains:";
for_each (myvector.begin(), myvector.end(), myobject);
std::cout << '\n';
return 0;
}
Output:
myvector contains: 10 20 30
myvector contains: 10 20 30
*/
// find and find_if.
//查找区间[first,last)内元素第一个与value值相等的元素，并返回其位置
//其中find函数是采用默认的equality操作operator==
//find_if是采用用户自行指定的操作pred
//若find函数萃取出来的迭代器类型为输入迭代器input_iterator_tag，则调用此函数
template
inline _InputIter find(_InputIter __first, _InputIter __last,
const _Tp& __val,
input_iterator_tag)
{//若尚未到达区间的尾端，且未找到匹配的值，则继续查找
while (__first != __last && !(*__first == __val))
++__first;
//若找到匹配的值，则返回该位置
//若找不到，即到达区间尾端，此时first=last，则返回first
return __first;
}
//若find_if函数萃取出来的迭代器类型为输入迭代器input_iterator_tag，则调用此函数
template
inline _InputIter find_if(_InputIter __first, _InputIter __last,
_Predicate __pred,
input_iterator_tag)
{//若尚未到达区间的尾端，且未找到匹配的值，则继续查找
while (__first != __last && !__pred(*__first))
++__first;
//若找到匹配的值，则返回该位置
//若找不到，即到达区间尾端，此时first=last，则返回first
return __first;
}
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
//若find函数萃取出来的迭代器类型为随机访问迭代器random_access_iterator_tag，则调用此函数
template
_RandomAccessIter find(_RandomAccessIter __first, _RandomAccessIter __last,
const _Tp& __val,
random_access_iterator_tag)
{
typename iterator_traits<_RandomAccessIter>::difference_type __trip_count
= (__last - __first) >> 2;
for ( ; __trip_count > 0 ; --__trip_count) {
if (*__first == __val) return __first;
++__first;
if (*__first == __val) return __first;
++__first;
if (*__first == __val) return __first;
++__first;
if (*__first == __val) return __first;
++__first;
}
switch(__last - __first) {
case 3:
if (*__first == __val) return __first;
++__first;
case 2:
if (*__first == __val) return __first;
++__first;
case 1:
if (*__first == __val) return __first;
++__first;
case 0:
default:
return __last;
}
}
//若find_if函数萃取出来的迭代器类型为随机访问迭代器random_access_iterator_tag，则调用此函数
template
_RandomAccessIter find_if(_RandomAccessIter __first, _RandomAccessIter __last,
_Predicate __pred,
random_access_iterator_tag)
{
typename iterator_traits<_RandomAccessIter>::difference_type __trip_count
= (__last - __first) >> 2;
for ( ; __trip_count > 0 ; --__trip_count) {
if (__pred(*__first)) return __first;
++__first;
if (__pred(*__first)) return __first;
++__first;
if (__pred(*__first)) return __first;
++__first;
if (__pred(*__first)) return __first;
++__first;
}
switch(__last - __first) {
case 3:
if (__pred(*__first)) return __first;
++__first;
case 2:
if (__pred(*__first)) return __first;
++__first;
case 1:
if (__pred(*__first)) return __first;
++__first;
case 0:
default:
return __last;
}
}
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
/*find函数功能：Returns an iterator to the first element in the range [first,last) that compares equal to val.
If no such element is found, the function returns last.
find函数原型：
template
InputIterator find (InputIterator first, InputIterator last, const T& val);
*/
//find函数对外接口
template
inline _InputIter find(_InputIter __first, _InputIter __last,
const _Tp& __val)
{
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_InputIter>::value_type, _Tp);
//首先萃取出first迭代器的类型，根据迭代器的类型调用不同的函数
return find(__first, __last, __val, __ITERATOR_CATEGORY(__first));
}
/*find_if函数功能：Returns an iterator to the first element in the range [first,last) for which pred returns true.
If no such element is found, the function returns last.
find_if函数原型：
template
InputIterator find_if (InputIterator first, InputIterator last, UnaryPredicate pred);
*/
//find_if 函数对外接口
template
inline _InputIter find_if(_InputIter __first, _InputIter __last,
_Predicate __pred) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_InputIter>::value_type);
//首先萃取出first迭代器的类型，根据迭代器的类型调用不同的函数
return find_if(__first, __last, __pred, __ITERATOR_CATEGORY(__first));
}
//find和find_if函数举例：
/*
#include // std::cout
#include // std::find_if
#include // std::vector
bool IsOdd (int i) {
return ((i%2)==1);
}
int main () {
std::vector myvector;
myvector.push_back(10);
myvector.push_back(25);
myvector.push_back(40);
myvector.push_back(55);
std::vector::iterator it = std::find_if (myvector.begin(), myvector.end(), IsOdd);
std::cout << "The first odd value is " << *it << '\n';
// using std::find with vector and iterator:
it = find (myvector.begin(), myvector.end(), 40);
if (it != myvector.end())
std::cout << "Element found in myvector: " << *it << '\n';
else
std::cout << "Element not found in myints\n";
return 0;
}
Output:
The first odd value is 25
Element found in myvector: 40
*/
// adjacent_find.
//查找区间[first,last)内第一次重复的相邻元素
//若存在返回相邻元素的第一个元素位置
//若不存在返回last位置
/*该函数有两个版本：第一版本是默认操作operator==；第二版本是用户指定的二元操作pred
函数对外接口的原型：
equality (1)：默认操作是operator==
template
ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last);
predicate (2)：用户指定的二元操作pred
template
ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last,
BinaryPredicate pred);
*/
//版本一：默认操作是operator==
template
_ForwardIter adjacent_find(_ForwardIter __first, _ForwardIter __last) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,
_EqualityComparable);
/*
情况1：若输入区间为空，则直接返回尾端last；
情况2：若输入区间不为空，且存在相邻重复元素，则返回相邻元素的第一个元素的位置；
情况3：若输入区间不为空，但是不存在相邻重复元素，则直接返回尾端last；
*/
//情况1：
if (__first == __last)//若输入区间为空
return __last;//直接返回last
//情况2：
_ForwardIter __next = __first;//定义当前位置的下一个位置(即当前元素的相邻元素)
while(++__next != __last) {//若还没到达尾端，执行while循环
if (*__first == *__next)//相邻元素值相等，则找到相邻重复元素
return __first;//返回第一个元素的位置
__first = __next;//若暂时找不到，则继续找，直到到达区间尾端
}
//情况3：
return __last;//直接返回尾端last
}
//版本二：用户指定的二元操作pred
//实现过程和版本一一样，只是判断规则不同
template
_ForwardIter adjacent_find(_ForwardIter __first, _ForwardIter __last,
_BinaryPredicate __binary_pred) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
typename iterator_traits<_ForwardIter>::value_type,
typename iterator_traits<_ForwardIter>::value_type);
if (__first == __last)
return __last;
_ForwardIter __next = __first;
while(++__next != __last) {
//如果找到相邻元素符合用户指定条件，就返回第一元素位置
if (__binary_pred(*__first, *__next))
return __first;
__first = __next;
}
return __last;
}
//adjacent_find函数举例：
/*
#include // std::cout
#include // std::adjacent_find
#include // std::vector
bool myfunction (int i, int j) {
return (i==j);
}
int main () {
int myints[] = {5,20,5,30,30,20,10,10,20};
std::vector myvector (myints,myints+8);
std::vector::iterator it;
// using default comparison:
it = std::adjacent_find (myvector.begin(), myvector.end());
if (it!=myvector.end())
std::cout << "the first pair of repeated elements are: " << *it << '\n';
//using predicate comparison:
it = std::adjacent_find (++it, myvector.end(), myfunction);
if (it!=myvector.end())
std::cout << "the second pair of repeated elements are: " << *it << '\n';
return 0;
}
Output:
the first pair of repeated elements are: 30
the second pair of repeated elements are: 10
*/
// count and count_if. There are two version of each, one whose return type
// type is void and one (present only if we have partial specialization)
// whose return type is iterator_traits<_InputIter>::difference_type. The
// C++ standard only has the latter version, but the former, which was present
// in the HP STL, is retained for backward compatibility.
//计算指定元素的个数
//SGI STL中提供两个版本，但是C++标准只提供一种版本
/*功能：Returns the number of elements in the range [first,last) that compare equal to val.
C++标准只提供一种count原型：
template
typename iterator_traits::difference_type
count (InputIterator first, InputIterator last, const T& val);
*/
//SGI STL提供的版本一count，不是C++标准：默认使用operator==
template
void count(_InputIter __first, _InputIter __last, const _Tp& __value,
_Size& __n) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(typename iterator_traits<_InputIter>::value_type,
_EqualityComparable);
__STL_REQUIRES(_Tp, _EqualityComparable);
//将区间[first,last)内的元素和指定值value比较
//若没到达区间尾端，继续查找
for ( ; __first != __last; ++__first)
if (*__first == __value)//若存在相等的值
++__n;//计数器累加1
}
/*功能：Returns the number of elements in the range [first,last) for which pred is true.
C++标准只提供一种count_if原型：
template
typename iterator_traits::difference_type
count_if (InputIterator first, InputIterator last, UnaryPredicate pred);
*/
//SGI STL提供的版本一count_if，不是C++标准：默认使用operator==
template
void count_if(_InputIter __first, _InputIter __last, _Predicate __pred,
_Size& __n) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_InputIter>::value_type);
//将区间[first,last)内的元素和指定值value比较
//若没到达区间尾端，继续查找
for ( ; __first != __last; ++__first)
if (__pred(*__first))//存在符合规则的元素
++__n;//计数器累加1
}
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
//SGI STL提供的版本二count，也C++标准提供的版本
template
typename iterator_traits<_InputIter>::difference_type
count(_InputIter __first, _InputIter __last, const _Tp& __value) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(typename iterator_traits<_InputIter>::value_type,
_EqualityComparable);
__STL_REQUIRES(_Tp, _EqualityComparable);
typename iterator_traits<_InputIter>::difference_type __n = 0;
//将区间[first,last)内的元素和指定值value比较
//若没到达区间尾端，继续查找
for ( ; __first != __last; ++__first)
if (*__first == __value)//存在相等的元素
++__n;//计数器累加1
return __n;
}
//SGI STL提供的版本二count_if，也C++标准提供的版本
template
typename iterator_traits<_InputIter>::difference_type
count_if(_InputIter __first, _InputIter __last, _Predicate __pred) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_InputIter>::value_type);
typename iterator_traits<_InputIter>::difference_type __n = 0;
//将区间[first,last)内的元素和指定值value比较
//若没到达区间尾端，继续查找
for ( ; __first != __last; ++__first)
if (__pred(*__first))//存在符合规则的元素
++__n;//计数器累加1
return __n;
}
//下面针对count和count_if函数举例：
/*
#include // std::cout
#include // std::count
#include // std::vector
bool IsOdd (int i) { return ((i%2)==1); }
int main () {
// counting elements in array:
int myints[] = {10,20,31,30,21,10,11,20}; // 8 elements
int mycount = std::count (myints, myints+8, 10);
std::cout << "10 appears " << mycount << " times.\n";
// counting elements in container:
std::vector myvector (myints, myints+8);
mycount = std::count (myvector.begin(), myvector.end(), 20);
std::cout << "20 appears " << mycount << " times.\n";
mycount = count_if (myvector.begin(), myvector.end(), IsOdd);
std::cout << "myvector contains " << mycount << " odd values.\n";
return 0;
}
Output:
10 appears 2 times.
20 appears 2 times.
myvector contains 3 odd values.
*/
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
// search.
//在序列一[first1,last1)所涵盖的区间中，查找序列二[first2,last2)的首次出现点
//该查找函数有两个版本：
//版本一：使用默认的equality操作operator==
//版本二：用户根据需要自行指定操作规则
/*search函数功能：Searches the range [first1,last1) for the first occurrence of the sequence defined by [first2,last2),
and returns an iterator to its first element, or last1 if no occurrences are found.
search函数的原型：
equality (1)：版本一
template
ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2);
predicate (2)：版本二
template
ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
ForwardIterator2 first2, ForwardIterator2 last2,
BinaryPredicate pred);
*/
//版本一：使用默认的equality操作operator==
template
_ForwardIter1 search(_ForwardIter1 __first1, _ForwardIter1 __last1,
_ForwardIter2 __first2, _ForwardIter2 __last2)
{
__STL_REQUIRES(_ForwardIter1, _ForwardIterator);
__STL_REQUIRES(_ForwardIter2, _ForwardIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_ForwardIter1>::value_type,
typename iterator_traits<_ForwardIter2>::value_type);
// Test for empty ranges
if (__first1 == __last1 || __first2 == __last2)
return __first1;
// Test for a pattern of length 1.
_ForwardIter2 __tmp(__first2);
++__tmp;
if (__tmp == __last2)
return find(__first1, __last1, *__first2);
// General case.
_ForwardIter2 __p1, __p;
__p1 = __first2; ++__p1;
_ForwardIter1 __current = __first1;
while (__first1 != __last1) {//若还没到达区间尾端
__first1 = find(__first1, __last1, *__first2);//查找*first2在区间[first1,last1)首次出现的位置
if (__first1 == __last1)//若在[first1,last1)中不存在*first2，即在[first1,last1)不存在子序列[first2,last2)
return __last1;//则直接返回区间尾端
__p = __p1;
__current = __first1;
if (++__current == __last1)//若[first1,last1)只有一个元素，即序列[first1,last1)小于序列[first2,last2)
return __last1;//不可能成为其子序列，返回last1
while (*__current == *__p) {//若两个序列相对应的值相同
if (++__p == __last2)//若序列[first2,last2)只有两个元素，且与序列一匹配
return __first1;//则返回匹配的首次位置
if (++__current == __last1)//若第一个序列小于第二个序列
return __last1;//返回last1
}
++__first1;
}
return __first1;
}
//版本二：用户根据需要自行指定操作规则
template
_ForwardIter1 search(_ForwardIter1 __first1, _ForwardIter1 __last1,
_ForwardIter2 __first2, _ForwardIter2 __last2,
_BinaryPred __predicate)
{
__STL_REQUIRES(_ForwardIter1, _ForwardIterator);
__STL_REQUIRES(_ForwardIter2, _ForwardIterator);
__STL_BINARY_FUNCTION_CHECK(_BinaryPred, bool,
typename iterator_traits<_ForwardIter1>::value_type,
typename iterator_traits<_ForwardIter2>::value_type);
// Test for empty ranges
if (__first1 == __last1 || __first2 == __last2)
return __first1;
// Test for a pattern of length 1.
_ForwardIter2 __tmp(__first2);
++__tmp;
if (__tmp == __last2) {
while (__first1 != __last1 && !__predicate(*__first1, *__first2))
++__first1;
return __first1;
}
// General case.
_ForwardIter2 __p1, __p;
__p1 = __first2; ++__p1;
_ForwardIter1 __current = __first1;
while (__first1 != __last1) {
while (__first1 != __last1) {
if (__predicate(*__first1, *__first2))
break;
++__first1;
}
while (__first1 != __last1 && !__predicate(*__first1, *__first2))
++__first1;
if (__first1 == __last1)
return __last1;
__p = __p1;
__current = __first1;
if (++__current == __last1) return __last1;
while (__predicate(*__current, *__p)) {
if (++__p == __last2)
return __first1;
if (++__current == __last1)
return __last1;
}
++__first1;
}
return __first1;
}
// search_n. Search for __count consecutive copies of __val.
//在序列[first,last)查找连续count个符合条件值value元素的位置
//该查找函数有两个版本：
//版本一：使用默认的equality操作operator==
//版本二：用户根据需要自行指定操作规则
/*search_n函数功能：Searches the range [first,last) for a sequence of count elements,
each comparing equal to val (or for which pred returns true).
search_n函数的原型：
equality (1)：版本一
template
ForwardIterator search_n (ForwardIterator first, ForwardIterator last,
Size count, const T& val);
predicate (2)：版本二
template
ForwardIterator search_n ( ForwardIterator first, ForwardIterator last,
Size count, const T& val, BinaryPredicate pred );
*/
//版本一：使用默认的equality操作operator==
template
_ForwardIter search_n(_ForwardIter __first, _ForwardIter __last,
_Integer __count, const _Tp& __val) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,
_EqualityComparable);
__STL_REQUIRES(_Tp, _EqualityComparable);
if (__count <= 0)
return __first;
else {//首先查找value第一次出现的位置
__first = find(__first, __last, __val);
while (__first != __last) {//若出现的位置不是区间尾端
_Integer __n = __count - 1;//更新个数，下面只需查找n=count-1个连续相同value即可
_ForwardIter __i = __first;
++__i;//从当前位置的下一个位置开始查找
//若没有到达区间尾端，且个数n大于0，且区间元素与value值相等
while (__i != __last && __n != 0 && *__i == __val) {
++__i;//继续查找
--__n;//减少查找的次数，因为已经找到value再次出现
}
if (__n == 0)//若区间尚未到达尾端，但是count个value已经查找到
return __first;//则输出查找到的首次出现value的位置
else
__first = find(__i, __last, __val);//若尚未找到连续count个value值的位置，则找出value下次出现的位置，并准备下一次while循环
}
return __last;
}
}
//版本二：用户根据需要自行指定操作规则
template
_ForwardIter search_n(_ForwardIter __first, _ForwardIter __last,
_Integer __count, const _Tp& __val,
_BinaryPred __binary_pred) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_BINARY_FUNCTION_CHECK(_BinaryPred, bool,
typename iterator_traits<_ForwardIter>::value_type, _Tp);
if (__count <= 0)
return __first;
else {
while (__first != __last) {
if (__binary_pred(*__first, __val))
break;
++__first;
}
while (__first != __last) {
_Integer __n = __count - 1;
_ForwardIter __i = __first;
++__i;
while (__i != __last && __n != 0 && __binary_pred(*__i, __val)) {
++__i;
--__n;
}
if (__n == 0)
return __first;
else {
while (__i != __last) {
if (__binary_pred(*__i, __val))
break;
++__i;
}
__first = __i;
}
}
return __last;
}
}
//search和search_n函数举例：
/*
#include // std::cout
#include // std::search_n
#include // std::vector
bool mypredicate (int i, int j) {
return (i==j);
}
int main () {
int myints[]={10,20,30,30,20,10,10,20};
std::vector myvector (myints,myints+8);
std::vector::iterator it;
// using default comparison:
it = std::search_n (myvector.begin(), myvector.end(), 2, 30);
if (it!=myvector.end())
std::cout << "two 30s found at position " << (it-myvector.begin()) << '\n';
else
std::cout << "match not found\n";
// using predicate comparison:
it = std::search_n (myvector.begin(), myvector.end(), 2, 10, mypredicate);
if (it!=myvector.end())
std::cout << "two 10s found at position " << int(it-myvector.begin()) << '\n';
else
std::cout << "match not found\n";
int needle1[] = {10,20};
// using default comparison:
it = std::search (myvector.begin(), myvector.end(), needle1, needle1+2);
if (it!=myvector.end())
std::cout << "needle1 found at position " << (it-myvector.begin()) << '\n';
else
std::cout << "needle1 not found\n";
// using predicate comparison:
int needle2[] = {30,20,10};
it = std::search (myvector.begin(), myvector.end(), needle2, needle2+3, mypredicate);
if (it!=myvector.end())
std::cout << "needle2 found at position " << (it-myvector.begin()) << '\n';
else
std::cout << "needle2 not found\n";
return 0;
}
Output:
two 30s found at position 2
two 10s found at position 5
needle1 found at position 0
needle2 found at position 3
*/
// swap_ranges
//将区间[first1,last1)内的元素与“从first2开始，个数相同”的元素相互交换
//这两个序列可位于同一容器，或不同容器
//如果第二序列小于第一序列长度，或者两序列在同一容器且重叠，则结果未可预期
//Exchanges the values of each of the elements in the range [first1,last1)
//with those of their respective elements in the range beginning at first2.
template
_ForwardIter2 swap_ranges(_ForwardIter1 __first1, _ForwardIter1 __last1,
_ForwardIter2 __first2) {
__STL_REQUIRES(_ForwardIter1, _Mutable_ForwardIterator);
__STL_REQUIRES(_ForwardIter2, _Mutable_ForwardIterator);
__STL_CONVERTIBLE(typename iterator_traits<_ForwardIter1>::value_type,
typename iterator_traits<_ForwardIter2>::value_type);
__STL_CONVERTIBLE(typename iterator_traits<_ForwardIter2>::value_type,
typename iterator_traits<_ForwardIter1>::value_type);
for ( ; __first1 != __last1; ++__first1, ++__first2)//遍历第一个序列
iter_swap(__first1, __first2);//交换迭代器所指的元素
return __first2;
}
//swap_ranges函数举例：
/*
#include // std::cout
#include // std::swap_ranges
#include // std::vector
int main () {
std::vector foo (5,10); // foo: 10 10 10 10 10
std::vector bar (5,33); // bar: 33 33 33 33 33
std::swap_ranges(foo.begin()+1, foo.end()-1, bar.begin());
// print out results of swap:
std::cout << "foo contains:";
for (std::vector::iterator it=foo.begin(); it!=foo.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
std::cout << "bar contains:";
for (std::vector::iterator it=bar.begin(); it!=bar.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
Output:
foo contains: 10 33 33 33 10
bar contains: 10 10 10 33 33
*/
// transform
//两个版本
/*
函数原型：
unary operation(1)：版本一
template
OutputIterator transform (InputIterator first1, InputIterator last1,
OutputIterator result, UnaryOperation op);
binary operation(2)：版本二
template
OutputIterator transform (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, OutputIterator result,
BinaryOperation binary_op);
函数功能：
(1) unary operation
Applies op to each of the elements in the range [first1,last1) and stores the value
returned by each operation in the range that begins at result.
(2) binary operation
Calls binary_op using each of the elements in the range [first1,last1) as first argument,
and the respective argument in the range that begins at first2 as second argument.
The value returned by each call is stored in the range that begins at result.
*/
//第一个版本：以仿函数opr作用于[first,last)中的每一个元素，并以其结果产生出一个新的序列
template
_OutputIter transform(_InputIter __first, _InputIter __last,
_OutputIter __result, _UnaryOperation __opr) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
for ( ; __first != __last; ++__first, ++__result)
*__result = __opr(*__first);
return __result;
}
//第二个版本：以仿函数binary_op作用于一双元素上（其中一个元素来自[first1,last1)，另一个元素来自“从first2开始的序列”）
//并以其结果产生出一个新的序列
template
_OutputIter transform(_InputIter1 __first1, _InputIter1 __last1,
_InputIter2 __first2, _OutputIter __result,
_BinaryOperation __binary_op) {
__STL_REQUIRES(_InputIter1, _InputIterator);
__STL_REQUIRES(_InputIter2, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
for ( ; __first1 != __last1; ++__first1, ++__first2, ++__result)
*__result = __binary_op(*__first1, *__first2);
return __result;
}
//transform函数举例：
/*
#include // std::vector
#include // std::plus
int op_increase (int i) { return ++i; }
int main () {
std::vector foo;
std::vector bar;
// set some values:
for (int i=1; i<6; i++)
foo.push_back (i*10); // foo: 10 20 30 40 50
bar.resize(foo.size()); // allocate space
std::transform (foo.begin(), foo.end(), bar.begin(), op_increase);
// bar: 11 21 31 41 51
std::cout << "bar contains:";
for (std::vector::iterator it=bar.begin(); it!=bar.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
// std::plus adds together its two arguments:
std::transform (foo.begin(), foo.end(), bar.begin(), foo.begin(), std::plus());
// foo: 21 41 61 81 101
std::cout << "foo contains:";
for (std::vector::iterator it=foo.begin(); it!=foo.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
Output:
bar contains: 11 21 31 41 51
foo contains: 21 41 61 81 101
*/
// replace, replace_if, replace_copy, replace_copy_if
//将区间[first,last)内的所有old_value都以new_value替代.
template
void replace(_ForwardIter __first, _ForwardIter __last,
const _Tp& __old_value, const _Tp& __new_value) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_ForwardIter>::value_type, _Tp);
__STL_CONVERTIBLE(_Tp, typename iterator_traits<_ForwardIter>::value_type);
for ( ; __first != __last; ++__first)
//将区间内所有old_value都以new_value替代.
if (*__first == __old_value)
*__first = __new_value;
}
//将区间[first,last)内的所有被pred判断为true的元素都以new_value替代.
template
void replace_if(_ForwardIter __first, _ForwardIter __last,
_Predicate __pred, const _Tp& __new_value) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_CONVERTIBLE(_Tp, typename iterator_traits<_ForwardIter>::value_type);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_ForwardIter>::value_type);
for ( ; __first != __last; ++__first)
if (__pred(*__first))//pred判断为true
*__first = __new_value;//修改其值
}
//将区间[first,last)内的所有old_value都以new_value替代.将新序列复制到result所指的容器中
//原始容器的内容并不会改变
template
_OutputIter replace_copy(_InputIter __first, _InputIter __last,
_OutputIter __result,
const _Tp& __old_value, const _Tp& __new_value) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_InputIter>::value_type, _Tp);
for ( ; __first != __last; ++__first, ++__result)
*__result = *__first == __old_value ? __new_value : *__first;
return __result;
}
//将区间[first,last)内的所有被pred判断为true的元素都以new_value替代.将新序列复制到result所指的容器中
//原始容器的内容并不会改变
template
_OutputIter replace_copy_if(_InputIter __first, _InputIter __last,
_OutputIter __result,
_Predicate __pred, const _Tp& __new_value) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_InputIter>::value_type);
for ( ; __first != __last; ++__first, ++__result)
*__result = __pred(*__first) ? __new_value : *__first;
return __result;
}
// generate and generate_n
//将仿函数gen的处理结果填充在[first, last)区间内所有元素上，所谓填写
//就是用迭代器所指元素的assignment操作
//注意：对于用户自定义类型要提供operator =()
template
void generate(_ForwardIter __first, _ForwardIter __last, _Generator __gen) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_GENERATOR_CHECK(_Generator,
typename iterator_traits<_ForwardIter>::value_type);
for ( ; __first != __last; ++__first)//遍历整个序列
*__first = __gen();
}
//将仿函数gen的处理结果填充在first开始的n个元素上，所谓填写
//就是用迭代器所指元素的assignment操作
template
_OutputIter generate_n(_OutputIter __first, _Size __n, _Generator __gen) {
__STL_REQUIRES(_OutputIter, _OutputIterator);
for ( ; __n > 0; --__n, ++__first)//只限于n个元素
*__first = __gen();
return __first;
}
//generate和generate_n函数举例：
/*
#include // std::cout
#include // std::generate_n
int current = 0;
int UniqueNumber () { return ++current; }
int main () {
int myarray[9];
std::generate_n (myarray, 9, UniqueNumber);
std::cout << "myarray contains:";
for (int i=0; i<9; ++i)
std::cout << ' ' << myarray[i];
std::cout << '\n';
std::cout <<"the value of current: "< myvector (6);
std::generate (myvector.begin(), myvector.end(), UniqueNumber);
std::cout << "myvector contains:";
for (std::vector::iterator it=myvector.begin(); it!=myvector.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
Output:
myarray contains: 1 2 3 4 5 6 7 8 9
the value of current: 9
myvector contains: 10 11 12 13 14 15
*/
// remove, remove_if, remove_copy, remove_copy_if
//移除[first,last)区间内所有与value值相等的元素，并不是真正的从容器中删除这些元素(原容器的内容不会改变)
//而是将结果复制到一个以result为起始位置的容器中。新容器可以与原容器重叠
template
_OutputIter remove_copy(_InputIter __first, _InputIter __last,
_OutputIter __result, const _Tp& __value) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_InputIter>::value_type, _Tp);
for ( ; __first != __last; ++__first)//遍历容器
if (!(*__first == __value)) {//如果不相等
*__result = *__first;//赋值给新容器
++__result;//新容器前进一个位置
}
return __result;
}
//移除[first,last)区间内被仿函数pred判断为true的元素,并不是真正的从容器中删除这些元素(原容器的内容不会改变)
//而是将结果复制到一个以result为起始位置的容器中。新容器可以与原容器重叠
template
_OutputIter remove_copy_if(_InputIter __first, _InputIter __last,
_OutputIter __result, _Predicate __pred) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_InputIter>::value_type);
for ( ; __first != __last; ++__first)//遍历容器
if (!__pred(*__first)) {//若pred判断为false
*__result = *__first;//赋值给新容器
++__result;//新容器前进一个位置
}
return __result;
}
//移除[first,last)区间内所有与value值相等的元素,该操作不会改变容器大小，只是容器中元素值改变
//即移除之后，重新整理容器的内容
template
_ForwardIter remove(_ForwardIter __first, _ForwardIter __last,
const _Tp& __value) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,
typename iterator_traits<_ForwardIter>::value_type, _Tp);
__STL_CONVERTIBLE(_Tp, typename iterator_traits<_ForwardIter>::value_type);
__first = find(__first, __last, __value);//利用顺序查找找出第一个与value相等的元素
_ForwardIter __i = __first;
//下面调用remove_copy
return __first == __last ? __first
: remove_copy(++__i, __last, __first, __value);
}
//移除[first,last)区间内所有被pred判断为true的元素,该操作不会改变容器大小，只是容器中元素值改变
//即移除之后，重新整理容器的内容
template
_ForwardIter remove_if(_ForwardIter __first, _ForwardIter __last,
_Predicate __pred) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_ForwardIter>::value_type);
__first = find_if(__first, __last, __pred);//利用顺序查找找出第一个与value相等的元素
_ForwardIter __i = __first;
//下面调用remove_copy_if
return __first == __last ? __first
: remove_copy_if(++__i, __last, __first, __pred);
}
//上面四个移除函数举例：
/*
#include // std::cout
#include // std::remove
bool IsOdd (int i) { return ((i%2)==1); }
int main () {
int myints[] = {10,20,31,30,20,11,10,20}; // 10 20 31 30 20 11 10 20
std::vector myvector (8);
std::remove_copy (myints,myints+8,myvector.begin(),20); // 10 31 30 11 10 0 0 0
std::cout << "myvector contains:";
for (std::vector::iterator it=myvector.begin(); it!=myvector.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
// bounds of range:
int* pbegin = myints; // ^
int* pend = myints+sizeof(myints)/sizeof(int); // ^ ^
pend = std::remove (pbegin, pend, 20); // 10 31 30 11 10 ? ? ?
// ^ ^
std::cout << "range contains:";
for (int* p=pbegin; p!=pend; ++p)
std::cout << ' ' << *p;
std::cout << '\n';
std::vector myvector2 (7);
std::remove_copy_if (myints,myints+7,myvector2.begin(),IsOdd);
std::cout << "myvector2 contains:";
for (std::vector::iterator it=myvector2.begin(); it!=myvector2.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
pend = std::remove_if (pbegin, pend, IsOdd); // 10 30 10 ? ? ? ? ?
// ^ ^
std::cout << "the range contains:";
for (int* p=pbegin; p!=pend; ++p)
std::cout << ' ' << *p;
std::cout << '\n';
return 0;
}
Output:
myvector contains: 10 31 30 11 10 0 0 0
range contains: 10 31 30 11 10
myvector2 contains: 10 30 10 10 0 0 0
the range contains: 10 30 10
*/
// unique and unique_copy
template
_OutputIter __unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result, _Tp*) {
_Tp __value = *__first;
*__result = __value;
while (++__first != __last)
if (!(__value == *__first)) {
__value = *__first;
*++__result = __value;
}
return ++__result;
}
//若result类型为output_iterator_tag，则调用该函数
template
inline _OutputIter __unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result,
output_iterator_tag) {
//判断first的value_type类型，根据不同类型调用不同函数
return __unique_copy(__first, __last, __result, __VALUE_TYPE(__first));
}
//若result类型为forward_iterator_tag，则调用该函数
template
_ForwardIter __unique_copy(_InputIter __first, _InputIter __last,
_ForwardIter __result, forward_iterator_tag) {
*__result = *__first;//记录第一个元素
while (++__first != __last)//遍历区间
//若不存在相邻重复元素，则继续记录到目标区result
if (!(*__result == *__first))
*++__result = *__first;//记录元素到目标区
return ++__result;
}
////unique_copy将区间[first,last)内元素复制到以result开头的区间上，但是如果存在相邻重复元素时，只复制其中第一个元素
//和unique一样，这里也有两个版本
/*
函数原型：
equality (1)
template
OutputIterator unique_copy (InputIterator first, InputIterator last,
OutputIterator result);
predicate (2)
template
OutputIterator unique_copy (InputIterator first, InputIterator last,
OutputIterator result, BinaryPredicate pred);
*/
//版本一
template
inline _OutputIter unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_REQUIRES(typename iterator_traits<_InputIter>::value_type,
_EqualityComparable);
if (__first == __last) return __result;
//根据result迭代器的类型，调用不同的函数
return __unique_copy(__first, __last, __result,
__ITERATOR_CATEGORY(__result));
}
template
_OutputIter __unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result,
_BinaryPredicate __binary_pred, _Tp*) {
__STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool, _Tp, _Tp);
_Tp __value = *__first;
*__result = __value;
while (++__first != __last)
if (!__binary_pred(__value, *__first)) {
__value = *__first;
*++__result = __value;
}
return ++__result;
}
template
inline _OutputIter __unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result,
_BinaryPredicate __binary_pred,
output_iterator_tag) {
return __unique_copy(__first, __last, __result, __binary_pred,
__VALUE_TYPE(__first));
}
template
_ForwardIter __unique_copy(_InputIter __first, _InputIter __last,
_ForwardIter __result,
_BinaryPredicate __binary_pred,
forward_iterator_tag) {
__STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
typename iterator_traits<_ForwardIter>::value_type,
typename iterator_traits<_InputIter>::value_type);
*__result = *__first;
while (++__first != __last)
if (!__binary_pred(*__result, *__first)) *++__result = *__first;
return ++__result;
}
//版本二
template
inline _OutputIter unique_copy(_InputIter __first, _InputIter __last,
_OutputIter __result,
_BinaryPredicate __binary_pred) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
if (__first == __last) return __result;
//根据result迭代器的类型，调用不同的函数
return __unique_copy(__first, __last, __result, __binary_pred,
__ITERATOR_CATEGORY(__result));
}
//移除区间[first,last)相邻连续重复的元素
//unique有两个版本
//功能：Removes all but the first element from every consecutive group of equivalent elements in the range [first,last).
/*
函数原型：
equality (1)：版本一采用operator==
template
ForwardIterator unique (ForwardIterator first, ForwardIterator last);
predicate (2)：版本二采用pred操作
template
ForwardIterator unique (ForwardIterator first, ForwardIterator last,
BinaryPredicate pred);
*/
//版本一
template
_ForwardIter unique(_ForwardIter __first, _ForwardIter __last) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,
_EqualityComparable);
__first = adjacent_find(__first, __last);//找出第一个相邻元素的起始位置
return unique_copy(__first, __last, __first);//调用unique_copy完成操作
}
//版本二
template
_ForwardIter unique(_ForwardIter __first, _ForwardIter __last,
_BinaryPredicate __binary_pred) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,
typename iterator_traits<_ForwardIter>::value_type,
typename iterator_traits<_ForwardIter>::value_type);
__first = adjacent_find(__first, __last, __binary_pred);//找出第一个相邻元素的起始位置
return unique_copy(__first, __last, __first, __binary_pred);//调用unique_copy完成操作
}
// reverse and reverse_copy, and their auxiliary functions
//若迭代器类型为bidirectional_iterator_tag，则调用此函数
template
void __reverse(_BidirectionalIter __first, _BidirectionalIter __last,
bidirectional_iterator_tag) {
while (true)
if (__first == __last || __first == --__last)//这里需注意，每次判断last迭代器都会后退一位
return;
else
iter_swap(__first++, __last);//单向交换迭代器所指的元素
}
//若迭代器类型为random_access_iterator_tag，则调用此函数
template
void __reverse(_RandomAccessIter __first, _RandomAccessIter __last,
random_access_iterator_tag) {
while (__first < __last)//遍历容器
iter_swap(__first++, --__last);//交换两端迭代器所指的元素
}
//将序列[first,last)的所有元素在原容器中颠倒重排
template
inline void reverse(_BidirectionalIter __first, _BidirectionalIter __last) {
__STL_REQUIRES(_BidirectionalIter, _Mutable_BidirectionalIterator);
//首先萃取出迭代器的类型
__reverse(__first, __last, __ITERATOR_CATEGORY(__first));
}
//行为类似reverse，但产生的新序列会被置于以result指出的容器中
template
_OutputIter reverse_copy(_BidirectionalIter __first,
_BidirectionalIter __last,
_OutputIter __result) {
__STL_REQUIRES(_BidirectionalIter, _BidirectionalIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
while (__first != __last) {//遍历容器
--__last;//尾端前移一个位置
*__result = *__last;//result容器的起始位置元素值为原始容器尾端元素值
++__result;//更新result，使其前进一个位置
}
return __result;
}
// rotate and rotate_copy, and their auxiliary functions
template
_EuclideanRingElement __gcd(_EuclideanRingElement __m,
_EuclideanRingElement __n)
{
while (__n != 0) {
_EuclideanRingElement __t = __m % __n;
__m = __n;
__n = __t;
}
return __m;
}
//迭代器类型为forward_iterator_tag，调用此函数
template
_ForwardIter __rotate(_ForwardIter __first,
_ForwardIter __middle,
_ForwardIter __last,
_Distance*,
forward_iterator_tag) {
if (__first == __middle)
return __last;
if (__last == __middle)
return __first;
_ForwardIter __first2 = __middle;
do {
swap(*__first++, *__first2++);
if (__first == __middle)
__middle = __first2;
} while (__first2 != __last);
_ForwardIter __new_middle = __first;
__first2 = __middle;
while (__first2 != __last) {
swap (*__first++, *__first2++);
if (__first == __middle)
__middle = __first2;
else if (__first2 == __last)
__first2 = __middle;
}
return __new_middle;
}
//迭代器类型为bidirectional_iterator_tag，调用此函数
template
_BidirectionalIter __rotate(_BidirectionalIter __first,
_BidirectionalIter __middle,
_BidirectionalIter __last,
_Distance*,
bidirectional_iterator_tag) {
__STL_REQUIRES(_BidirectionalIter, _Mutable_BidirectionalIterator);
if (__first == __middle)
return __last;
if (__last == __middle)
return __first;
__reverse(__first, __middle, bidirectional_iterator_tag());
__reverse(__middle, __last, bidirectional_iterator_tag());
while (__first != __middle && __middle != __last)
swap (*__first++, *--__last);
if (__first == __middle) {
__reverse(__middle, __last, bidirectional_iterator_tag());
return __last;
}
else {
__reverse(__first, __middle, bidirectional_iterator_tag());
return __first;
}
}
//迭代器类型为Random_iterator_tag，调用此函数
template
_RandomAccessIter __rotate(_RandomAccessIter __first,
_RandomAccessIter __middle,
_RandomAccessIter __last,
_Distance *, _Tp *) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
_Distance __n = __last - __first;
_Distance __k = __middle - __first;
_Distance __l = __n - __k;
_RandomAccessIter __result = __first + (__last - __middle);
if (__k == 0)
return __last;
else if (__k == __l) {
swap_ranges(__first, __middle, __middle);
return __result;
}
_Distance __d = __gcd(__n, __k);
for (_Distance __i = 0; __i < __d; __i++) {
_Tp __tmp = *__first;
_RandomAccessIter __p = __first;
if (__k < __l) {
for (_Distance __j = 0; __j < __l/__d; __j++) {
if (__p > __first + __l) {
*__p = *(__p - __l);
__p -= __l;
}
*__p = *(__p + __k);
__p += __k;
}
}
else {
for (_Distance __j = 0; __j < __k/__d - 1; __j ++) {
if (__p < __last - __k) {
*__p = *(__p + __k);
__p += __k;
}
*__p = * (__p - __l);
__p -= __l;
}
}
*__p = __tmp;
++__first;
}
return __result;
}
//将区间[first,middle)内的元素和[middle,last)内的元素互换。minddle所指的元素会成为容器的第一个元素
//例如对序列{1,2,3,4,5,6,7}，对元素3进行旋转操作,则结果为{3,4,5,6,7,1,2}
template
inline _ForwardIter rotate(_ForwardIter __first, _ForwardIter __middle,
_ForwardIter __last) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
//萃取出迭代器的类型，根据迭代器的类型调用不同的函数
return __rotate(__first, __middle, __last,
__DISTANCE_TYPE(__first),
__ITERATOR_CATEGORY(__first));
}
//将区间[first,middle)内的元素和[middle,last)内的元素互换。minddle所指的元素会成为新容器result的第一个元素
template
_OutputIter rotate_copy(_ForwardIter __first, _ForwardIter __middle,
_ForwardIter __last, _OutputIter __result) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
//这里直接采用复制操作，先把[middle,last)复制到result容器中，
//再把[first,middle)内容复制到result容器中
return copy(__first, __middle, copy(__middle, __last, __result));
}
// Return a random number in the range [0, __n). This function encapsulates
// whether we're using rand (part of the standard C library) or lrand48
// (not standard, but a much better choice whenever it's available).
template
inline _Distance __random_number(_Distance __n) {
#ifdef __STL_NO_DRAND48
return rand() % __n;
#else
return lrand48() % __n;
#endif
}
// random_shuffle
//将区间[first,last)内的元素随机重排
//两个版本的不同是随机数的取得
//版本一是使用内部随机数产生器
//版本二是使用一个会产生随机数的仿函数
/*
函数功能：Rearranges the elements in the range [first,last) randomly.
函数原型：
generator by default (1)
template
void random_shuffle (RandomAccessIterator first, RandomAccessIterator last);
specific generator (2)
template
void random_shuffle (RandomAccessIterator first, RandomAccessIterator last,
RandomNumberGenerator& gen);
*/
//版本一
template
inline void random_shuffle(_RandomAccessIter __first,
_RandomAccessIter __last) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
if (__first == __last) return;
for (_RandomAccessIter __i = __first + 1; __i != __last; ++__i)
iter_swap(__i, __first + __random_number((__i - __first) + 1));
}
//版本二
template
void random_shuffle(_RandomAccessIter __first, _RandomAccessIter __last,
_RandomNumberGenerator& __rand) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
if (__first == __last) return;
for (_RandomAccessIter __i = __first + 1; __i != __last; ++__i)
iter_swap(__i, __first + __rand((__i - __first) + 1));
}
// random_sample and random_sample_n (extensions, not part of the standard).
template
_OutputIter random_sample_n(_ForwardIter __first, _ForwardIter __last,
_OutputIter __out, const _Distance __n)
{
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
_Distance __remaining = 0;
distance(__first, __last, __remaining);
_Distance __m = min(__n, __remaining);
while (__m > 0) {
if (__random_number(__remaining) < __m) {
*__out = *__first;
++__out;
--__m;
}
--__remaining;
++__first;
}
return __out;
}
template
_OutputIter random_sample_n(_ForwardIter __first, _ForwardIter __last,
_OutputIter __out, const _Distance __n,
_RandomNumberGenerator& __rand)
{
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_UNARY_FUNCTION_CHECK(_RandomNumberGenerator, _Distance, _Distance);
_Distance __remaining = 0;
distance(__first, __last, __remaining);
_Distance __m = min(__n, __remaining);
while (__m > 0) {
if (__rand(__remaining) < __m) {
*__out = *__first;
++__out;
--__m;
}
--__remaining;
++__first;
}
return __out;
}
template
_RandomAccessIter __random_sample(_InputIter __first, _InputIter __last,
_RandomAccessIter __out,
const _Distance __n)
{
_Distance __m = 0;
_Distance __t = __n;
for ( ; __first != __last && __m < __n; ++__m, ++__first)
__out[__m] = *__first;
while (__first != __last) {
++__t;
_Distance __M = __random_number(__t);
if (__M < __n)
__out[__M] = *__first;
++__first;
}
return __out + __m;
}
template
_RandomAccessIter __random_sample(_InputIter __first, _InputIter __last,
_RandomAccessIter __out,
_RandomNumberGenerator& __rand,
const _Distance __n)
{
__STL_UNARY_FUNCTION_CHECK(_RandomNumberGenerator, _Distance, _Distance);
_Distance __m = 0;
_Distance __t = __n;
for ( ; __first != __last && __m < __n; ++__m, ++__first)
__out[__m] = *__first;
while (__first != __last) {
++__t;
_Distance __M = __rand(__t);
if (__M < __n)
__out[__M] = *__first;
++__first;
}
return __out + __m;
}
template
inline _RandomAccessIter
random_sample(_InputIter __first, _InputIter __last,
_RandomAccessIter __out_first, _RandomAccessIter __out_last)
{
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
return __random_sample(__first, __last,
__out_first, __out_last - __out_first);
}
template
inline _RandomAccessIter
random_sample(_InputIter __first, _InputIter __last,
_RandomAccessIter __out_first, _RandomAccessIter __out_last,
_RandomNumberGenerator& __rand)
{
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
return __random_sample(__first, __last,
__out_first, __rand,
__out_last - __out_first);
}
// partition, stable_partition, and their auxiliary functions
//若迭代器的类型为forward_iterator_tag，则调用此函数
template
_ForwardIter __partition(_ForwardIter __first,
_ForwardIter __last,
_Predicate __pred,
forward_iterator_tag) {
if (__first == __last) return __first;//若为空，直接退出
while (__pred(*__first))//若pred出first的值为true
if (++__first == __last) return __first;//先移动迭代器first，在判断是否到达尾端last
_ForwardIter __next = __first;//继续判断
while (++__next != __last)//若下一个位置依然不是尾端
if (__pred(*__next)) {//继续pred出next的值，若为true
swap(*__first, *__next);//交换值
++__first;//继续下一位置
}
return __first;
}
//若迭代器的类型为bidirectional_iterator_tag，则调用此函数
template
_BidirectionalIter __partition(_BidirectionalIter __first,
_BidirectionalIter __last,
_Predicate __pred,
bidirectional_iterator_tag) {
while (true) {
while (true)
if (__first == __last)//若为空
return __first;//直接退出
else if (__pred(*__first))//first的值符合不移动条件，则不移动该值
++__first;//只移动迭代器
else//若头指针符合移动
break;//跳出循环
--__last;//尾指针回溯
while (true)
if (__first == __last)//头指针等于尾指针
return __first;//操作结束
else if (!__pred(*__last))//尾指针的元素符合不移动操作
--__last;//至移动迭代器，并不移动具体元素
else//尾指针的元素符合移动操作
break;//跳出循环
iter_swap(__first, __last);//头尾指针交换元素
++__first;//准备下一次循环
}
}
//将区间[first,last)的元素进行排序，被pred判断为true的放在区间的前段，判定为false的放在区间后段
//该算算可能会使元素的元素位置放生改变.
/*
算法功能：Rearranges the elements from the range [first,last), in such a way that all the elements
for which pred returns true precede all those for which it returns false.
The iterator returned points to the first element of the second group.
算法原型：
template
BidirectionalIterator partition (BidirectionalIterator first,
BidirectionalIterator last, UnaryPredicate pred);
*/
template
inline _ForwardIter partition(_ForwardIter __first,
_ForwardIter __last,
_Predicate __pred) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_ForwardIter>::value_type);
//首先萃取出迭代器first的类型，根据迭代器的类型调用不同的函数
return __partition(__first, __last, __pred, __ITERATOR_CATEGORY(__first));
}
//partition函数举例：
/*
#include // std::cout
#include // std::partition
#include // std::vector
bool IsOdd (int i) { return (i%2)==1; }
int main () {
std::vector myvector;
// set some values:
for (int i=1; i<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9
std::vector::iterator bound;
bound = std::partition (myvector.begin(), myvector.end(), IsOdd);
// print out content:
std::cout << "odd elements:";
for (std::vector::iterator it=myvector.begin(); it!=bound; ++it)
std::cout << ' ' << *it;
std::cout << '\n';
std::cout << "even elements:";
for (std::vector::iterator it=bound; it!=myvector.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
Output:
odd elements: 1 9 3 7 5
even elements: 6 4 8 2
*/
template
_ForwardIter __inplace_stable_partition(_ForwardIter __first,
_ForwardIter __last,
_Predicate __pred, _Distance __len) {
if (__len == 1)
return __pred(*__first) ? __last : __first;
_ForwardIter __middle = __first;
advance(__middle, __len / 2);
return rotate(__inplace_stable_partition(__first, __middle, __pred,
__len / 2),
__middle,
__inplace_stable_partition(__middle, __last, __pred,
__len - __len / 2));
}
template
_ForwardIter __stable_partition_adaptive(_ForwardIter __first,
_ForwardIter __last,
_Predicate __pred, _Distance __len,
_Pointer __buffer,
_Distance __buffer_size)
{
if (__len <= __buffer_size) {
_ForwardIter __result1 = __first;
_Pointer __result2 = __buffer;
for ( ; __first != __last ; ++__first)
if (__pred(*__first)) {
*__result1 = *__first;
++__result1;
}
else {
*__result2 = *__first;
++__result2;
}
copy(__buffer, __result2, __result1);
return __result1;
}
else {
_ForwardIter __middle = __first;
advance(__middle, __len / 2);
return rotate(__stable_partition_adaptive(
__first, __middle, __pred,
__len / 2, __buffer, __buffer_size),
__middle,
__stable_partition_adaptive(
__middle, __last, __pred,
__len - __len / 2, __buffer, __buffer_size));
}
}
template
inline _ForwardIter
__stable_partition_aux(_ForwardIter __first, _ForwardIter __last,
_Predicate __pred, _Tp*, _Distance*)
{
_Temporary_buffer<_ForwardIter, _Tp> __buf(__first, __last);
if (__buf.size() > 0)
return __stable_partition_adaptive(__first, __last, __pred,
_Distance(__buf.requested_size()),
__buf.begin(), __buf.size());
else
return __inplace_stable_partition(__first, __last, __pred,
_Distance(__buf.requested_size()));
}
template
inline _ForwardIter stable_partition(_ForwardIter __first,
_ForwardIter __last,
_Predicate __pred) {
__STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);
__STL_UNARY_FUNCTION_CHECK(_Predicate, bool,
typename iterator_traits<_ForwardIter>::value_type);
if (__first == __last)
return __first;
else
return __stable_partition_aux(__first, __last, __pred,
__VALUE_TYPE(__first),
__DISTANCE_TYPE(__first));
}
//找出快速排序的枢纽位置
//版本一采用operator<
template
_RandomAccessIter __unguarded_partition(_RandomAccessIter __first,
_RandomAccessIter __last,
_Tp __pivot)
{
//找出枢纽轴的位置
//令头端迭代器向尾端方向移动，尾端迭代器向头端移动。
//当*first不小于枢纽值时，就停下来，当*last不大于枢纽值时也停下来，然后检测两个迭代器是否交错
//如果first仍然在左侧而last仍然在右侧，就交换两个元素，然后各自调整位置，向中央逼近，再继续执行相同的行为.
//直到first和last两个迭代器交错，此时表示已找到枢纽轴位置即first所在的位置
while (true) {
while (*__first < __pivot)
++__first;//first向尾端移动，直到遇到不小于枢纽值时，停止
--__last;
while (__pivot < *__last)
--__last;//last向头端移动，直到遇到不大于枢纽值时，停止
if (!(__first < __last))//检测两个迭代器是否交错
return __first;//交错，则此时已找到，即为first迭代器所指位置
iter_swap(__first, __last);//否则交换迭代器所指的元素
++__first;//继续执行相同行为
}
}
//版本一采用__comp
template
_RandomAccessIter __unguarded_partition(_RandomAccessIter __first,
_RandomAccessIter __last,
_Tp __pivot, _Compare __comp)
{
while (true) {
while (__comp(*__first, __pivot))
++__first;
--__last;
while (__comp(__pivot, *__last))
--__last;
if (!(__first < __last))
return __first;
iter_swap(__first, __last);
++__first;
}
}
const int __stl_threshold = 16;
// sort() and its auxiliary functions.
//__insertion_sort版本一的辅助函数
template
void __unguarded_linear_insert(_RandomAccessIter __last, _Tp __val) {
_RandomAccessIter __next = __last;
--__next;
//__insertion_sort的内循环
//注意：一旦不再出现逆转对，循环就结束
while (__val < *__next) {//存在逆转对
*__last = *__next;//调整元素
__last = __next;//调整迭代器
--__next;//左移一个位置
}
*__last = __val;//value的正确插入位置
}
//__insertion_sort版本二的辅助函数
template
void __unguarded_linear_insert(_RandomAccessIter __last, _Tp __val,
_Compare __comp) {
_RandomAccessIter __next = __last;
--__next;
while (__comp(__val, *__next)) {
*__last = *__next;
__last = __next;
--__next;
}
*__last = __val;
}
//__insertion_sort版本一的辅助函数
template
inline void __linear_insert(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*) {
_Tp __val = *__last;//记录尾元素
if (__val < *__first) {//尾元素比头元素还小
//将整个区间向右移一个位置
copy_backward(__first, __last, __last + 1);
*__first = __val;//令头元素等于原先的尾元素
//以上两行命令的功能相等于交换两个元素
}
else//尾元素不小于头元素
__unguarded_linear_insert(__last, __val);
}
//__insertion_sort版本二的辅助函数
template
inline void __linear_insert(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*, _Compare __comp) {
_Tp __val = *__last;
if (__comp(__val, *__first)) {
copy_backward(__first, __last, __last + 1);
*__first = __val;
}
else
__unguarded_linear_insert(__last, __val, __comp);
}
//__insertion_sort以双层循环形式进行。外循环遍历整个序列，每次迭代决定出一个子区间；
//内循环遍历子区间，将子区间内的每一个“逆转对”倒转过来，如果一旦不存在“逆转对”，表示排序完毕。
//“逆转对”概念：指任何两个迭代器i和j，i*j.
//版本一
template
void __insertion_sort(_RandomAccessIter __first, _RandomAccessIter __last) {
if (__first == __last) return; //若区间为空，则退出
for (_RandomAccessIter __i = __first + 1; __i != __last; ++__i)//外循环，遍历整个区间
//[first,i)形成的子空间
__linear_insert(__first, __i, __VALUE_TYPE(__first));
}
//版本二
template
void __insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last, _Compare __comp) {
if (__first == __last) return;
for (_RandomAccessIter __i = __first + 1; __i != __last; ++__i)
__linear_insert(__first, __i, __VALUE_TYPE(__first), __comp);
}
template
void __unguarded_insertion_sort_aux(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*) {
for (_RandomAccessIter __i = __first; __i != __last; ++__i)
__unguarded_linear_insert(__i, _Tp(*__i));
}
//sort版本一的辅助函数
template
inline void __unguarded_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last) {
__unguarded_insertion_sort_aux(__first, __last, __VALUE_TYPE(__first));
}
template
void __unguarded_insertion_sort_aux(_RandomAccessIter __first,
_RandomAccessIter __last,
_Tp*, _Compare __comp) {
for (_RandomAccessIter __i = __first; __i != __last; ++__i)
__unguarded_linear_insert(__i, _Tp(*__i), __comp);
}
template
inline void __unguarded_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last,
_Compare __comp) {
__unguarded_insertion_sort_aux(__first, __last, __VALUE_TYPE(__first),
__comp);
}
//sort版本一的辅助函数
template
void __final_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last) {
if (__last - __first > __stl_threshold) {//判断元素个数是否大于16
//则把区间分割成两段，一端长度为16，另一端为剩余的长度
__insertion_sort(__first, __first + __stl_threshold);
__unguarded_insertion_sort(__first + __stl_threshold, __last);
}
else//若不大于16，直接调用插入排序
__insertion_sort(__first, __last);
}
template
void __final_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last, _Compare __comp) {
if (__last - __first > __stl_threshold) {
__insertion_sort(__first, __first + __stl_threshold, __comp);
__unguarded_insertion_sort(__first + __stl_threshold, __last, __comp);
}
else
__insertion_sort(__first, __last, __comp);
}
//_lg()函数是用来控制分割恶化的情况
//该函数找出2^k <= n 的最大值k;
//例如：n=7,得k=2; n=20,得k=4; n=8,得k=3;
template
inline _Size __lg(_Size __n) {
_Size __k;
for (__k = 0; __n != 1; __n >>= 1) ++__k;
return __k;
}
//sort版本一的辅助函数
//参数__depth_limit表示最大的分割层数
template
void __introsort_loop(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*,
_Size __depth_limit)
{
//__stl_threshold为全局常量，其值为16
while (__last - __first > __stl_threshold) {//若区间长度大于16
if (__depth_limit == 0) {//表示分割恶化
partial_sort(__first, __last, __last);//转而调用堆排序heap_sort()
return;
}
--__depth_limit;
//计算分割点cut，枢纽值是采用首、尾、中央三个的中间值
_RandomAccessIter __cut =
__unguarded_partition(__first, __last,
_Tp(__median(*__first,
*(__first + (__last - __first)/2),
*(__last - 1))));
//对右半部分递归地进行排序
__introsort_loop(__cut, __last, (_Tp*) 0, __depth_limit);
__last = __cut;//接下来对左半部分递归地进行排序
}
}
template
void __introsort_loop(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*,
_Size __depth_limit, _Compare __comp)
{
while (__last - __first > __stl_threshold) {
if (__depth_limit == 0) {
partial_sort(__first, __last, __last, __comp);
return;
}
--__depth_limit;
_RandomAccessIter __cut =
__unguarded_partition(__first, __last,
_Tp(__median(*__first,
*(__first + (__last - __first)/2),
*(__last - 1), __comp)),
__comp);
__introsort_loop(__cut, __last, (_Tp*) 0, __depth_limit, __comp);
__last = __cut;
}
}
//SGI STL的排序算法，迭代器参数的类型必须是随机访问迭代器_RandomAccessIter
/*
函数功能：Sorts the elements in the range [first,last) into ascending order.
函数原型：
default (1) ：版本一采用默认的operator<
template
void sort (RandomAccessIterator first, RandomAccessIterator last);
custom (2) ：版本二采用仿函数comp
template
void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);
*/
//版本一
template
inline void sort(_RandomAccessIter __first, _RandomAccessIter __last) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_REQUIRES(typename iterator_traits<_RandomAccessIter>::value_type,
_LessThanComparable);
//_lg()函数是用来控制分割恶化的情况
if (__first != __last) {
__introsort_loop(__first, __last,
__VALUE_TYPE(__first),
__lg(__last - __first) * 2);
//进行插入排序
__final_insertion_sort(__first, __last);
}
}
//版本二
template
inline void sort(_RandomAccessIter __first, _RandomAccessIter __last,
_Compare __comp) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_RandomAccessIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
if (__first != __last) {
__introsort_loop(__first, __last,
__VALUE_TYPE(__first),
__lg(__last - __first) * 2,
__comp);
__final_insertion_sort(__first, __last, __comp);
}
}
// stable_sort() and its auxiliary functions.
template
void __inplace_stable_sort(_RandomAccessIter __first,
_RandomAccessIter __last) {
if (__last - __first < 15) {
__insertion_sort(__first, __last);
return;
}
_RandomAccessIter __middle = __first + (__last - __first) / 2;
__inplace_stable_sort(__first, __middle);
__inplace_stable_sort(__middle, __last);
__merge_without_buffer(__first, __middle, __last,
__middle - __first,
__last - __middle);
}
template
void __inplace_stable_sort(_RandomAccessIter __first,
_RandomAccessIter __last, _Compare __comp) {
if (__last - __first < 15) {
__insertion_sort(__first, __last, __comp);
return;
}
_RandomAccessIter __middle = __first + (__last - __first) / 2;
__inplace_stable_sort(__first, __middle, __comp);
__inplace_stable_sort(__middle, __last, __comp);
__merge_without_buffer(__first, __middle, __last,
__middle - __first,
__last - __middle,
__comp);
}
template
void __merge_sort_loop(_RandomAccessIter1 __first,
_RandomAccessIter1 __last,
_RandomAccessIter2 __result, _Distance __step_size) {
_Distance __two_step = 2 * __step_size;
while (__last - __first >= __two_step) {
__result = merge(__first, __first + __step_size,
__first + __step_size, __first + __two_step,
__result);
__first += __two_step;
}
__step_size = min(_Distance(__last - __first), __step_size);
merge(__first, __first + __step_size, __first + __step_size, __last,
__result);
}
template
void __merge_sort_loop(_RandomAccessIter1 __first,
_RandomAccessIter1 __last,
_RandomAccessIter2 __result, _Distance __step_size,
_Compare __comp) {
_Distance __two_step = 2 * __step_size;
while (__last - __first >= __two_step) {
__result = merge(__first, __first + __step_size,
__first + __step_size, __first + __two_step,
__result,
__comp);
__first += __two_step;
}
__step_size = min(_Distance(__last - __first), __step_size);
merge(__first, __first + __step_size,
__first + __step_size, __last,
__result,
__comp);
}
const int __stl_chunk_size = 7;
template
void __chunk_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last, _Distance __chunk_size)
{
while (__last - __first >= __chunk_size) {
__insertion_sort(__first, __first + __chunk_size);
__first += __chunk_size;
}
__insertion_sort(__first, __last);
}
template
void __chunk_insertion_sort(_RandomAccessIter __first,
_RandomAccessIter __last,
_Distance __chunk_size, _Compare __comp)
{
while (__last - __first >= __chunk_size) {
__insertion_sort(__first, __first + __chunk_size, __comp);
__first += __chunk_size;
}
__insertion_sort(__first, __last, __comp);
}
template
void __merge_sort_with_buffer(_RandomAccessIter __first,
_RandomAccessIter __last,
_Pointer __buffer, _Distance*) {
_Distance __len = __last - __first;
_Pointer __buffer_last = __buffer + __len;
_Distance __step_size = __stl_chunk_size;
__chunk_insertion_sort(__first, __last, __step_size);
while (__step_size < __len) {
__merge_sort_loop(__first, __last, __buffer, __step_size);
__step_size *= 2;
__merge_sort_loop(__buffer, __buffer_last, __first, __step_size);
__step_size *= 2;
}
}
template
void __merge_sort_with_buffer(_RandomAccessIter __first,
_RandomAccessIter __last, _Pointer __buffer,
_Distance*, _Compare __comp) {
_Distance __len = __last - __first;
_Pointer __buffer_last = __buffer + __len;
_Distance __step_size = __stl_chunk_size;
__chunk_insertion_sort(__first, __last, __step_size, __comp);
while (__step_size < __len) {
__merge_sort_loop(__first, __last, __buffer, __step_size, __comp);
__step_size *= 2;
__merge_sort_loop(__buffer, __buffer_last, __first, __step_size, __comp);
__step_size *= 2;
}
}
template
void __stable_sort_adaptive(_RandomAccessIter __first,
_RandomAccessIter __last, _Pointer __buffer,
_Distance __buffer_size) {
_Distance __len = (__last - __first + 1) / 2;
_RandomAccessIter __middle = __first + __len;
if (__len > __buffer_size) {
__stable_sort_adaptive(__first, __middle, __buffer, __buffer_size);
__stable_sort_adaptive(__middle, __last, __buffer, __buffer_size);
}
else {
__merge_sort_with_buffer(__first, __middle, __buffer, (_Distance*)0);
__merge_sort_with_buffer(__middle, __last, __buffer, (_Distance*)0);
}
__merge_adaptive(__first, __middle, __last, _Distance(__middle - __first),
_Distance(__last - __middle), __buffer, __buffer_size);
}
template
void __stable_sort_adaptive(_RandomAccessIter __first,
_RandomAccessIter __last, _Pointer __buffer,
_Distance __buffer_size, _Compare __comp) {
_Distance __len = (__last - __first + 1) / 2;
_RandomAccessIter __middle = __first + __len;
if (__len > __buffer_size) {
__stable_sort_adaptive(__first, __middle, __buffer, __buffer_size,
__comp);
__stable_sort_adaptive(__middle, __last, __buffer, __buffer_size,
__comp);
}
else {
__merge_sort_with_buffer(__first, __middle, __buffer, (_Distance*)0,
__comp);
__merge_sort_with_buffer(__middle, __last, __buffer, (_Distance*)0,
__comp);
}
__merge_adaptive(__first, __middle, __last, _Distance(__middle - __first),
_Distance(__last - __middle), __buffer, __buffer_size,
__comp);
}
template
inline void __stable_sort_aux(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*, _Distance*) {
_Temporary_buffer<_RandomAccessIter, _Tp> buf(__first, __last);
if (buf.begin() == 0)
__inplace_stable_sort(__first, __last);
else
__stable_sort_adaptive(__first, __last, buf.begin(),
_Distance(buf.size()));
}
template
inline void __stable_sort_aux(_RandomAccessIter __first,
_RandomAccessIter __last, _Tp*, _Distance*,
_Compare __comp) {
_Temporary_buffer<_RandomAccessIter, _Tp> buf(__first, __last);
if (buf.begin() == 0)
__inplace_stable_sort(__first, __last, __comp);
else
__stable_sort_adaptive(__first, __last, buf.begin(),
_Distance(buf.size()),
__comp);
}
template
inline void stable_sort(_RandomAccessIter __first,
_RandomAccessIter __last) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_REQUIRES(typename iterator_traits<_RandomAccessIter>::value_type,
_LessThanComparable);
__stable_sort_aux(__first, __last,
__VALUE_TYPE(__first),
__DISTANCE_TYPE(__first));
}
template
inline void stable_sort(_RandomAccessIter __first,
_RandomAccessIter __last, _Compare __comp) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_RandomAccessIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
__stable_sort_aux(__first, __last,
__VALUE_TYPE(__first),
__DISTANCE_TYPE(__first),
__comp);
}
// partial_sort, partial_sort_copy, and auxiliary functions.
//重新安排序列[first,last)，使序列前半部分middle-first个最小元素以递增顺序排序，并将其置于[first,middle)
//其余last-middle个元素不指定任何排序，并将其置于[middle,last)
//注意：迭代器middle是在[first,last)范围之内
/*
函数功能：Rearranges the elements in the range [first,last),
in such a way that the elements before middle are the smallest elements in the entire range
and are sorted in ascending order, while the remaining elements are left without any specific order.
函数原型：
default (1) 版本一 operator<
template
void partial_sort (RandomAccessIterator first, RandomAccessIterator middle,
RandomAccessIterator last);
custom (2) 版本二 comp
template
void partial_sort (RandomAccessIterator first, RandomAccessIterator middle,
RandomAccessIterator last, Compare comp);
*/
template
void __partial_sort(_RandomAccessIter __first, _RandomAccessIter __middle,
_RandomAccessIter __last, _Tp*) {
//利用heap的知识，在SGI STL中，是采用最大堆
//将[first,middle)区间的元素创建成最大堆
//再根据最大堆的性质，一个一个弹出堆，并将其保存，即堆排序
make_heap(__first, __middle);//创建最大堆，定义与文件
//以下是在区间中[first,last)找出middle-first个最小元素
//这里的是将后半部分[middle,last)的元素依次与最大堆的根节点元素(即堆的最大元素)比较
//若小于堆的最大元素，则与堆的最大元素交换，并调整堆，使其依次成为最大堆
//若不小于堆的最大元素，则不作任何操作
for (_RandomAccessIter __i = __middle; __i < __last; ++__i)
if (*__i < *__first)
__pop_heap(__first, __middle, __i, _Tp(*__i),
__DISTANCE_TYPE(__first));
sort_heap(__first, __middle);//对最大堆进行堆排序
}
//版本一
template
inline void partial_sort(_RandomAccessIter __first,
_RandomAccessIter __middle,
_RandomAccessIter __last) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_REQUIRES(typename iterator_traits<_RandomAccessIter>::value_type,
_LessThanComparable);
__partial_sort(__first, __middle, __last, __VALUE_TYPE(__first));
}
template
void __partial_sort(_RandomAccessIter __first, _RandomAccessIter __middle,
_RandomAccessIter __last, _Tp*, _Compare __comp) {
make_heap(__first, __middle, __comp);
for (_RandomAccessIter __i = __middle; __i < __last; ++__i)
if (__comp(*__i, *__first))
__pop_heap(__first, __middle, __i, _Tp(*__i), __comp,
__DISTANCE_TYPE(__first));
sort_heap(__first, __middle, __comp);
}
//版本二
template
inline void partial_sort(_RandomAccessIter __first,
_RandomAccessIter __middle,
_RandomAccessIter __last, _Compare __comp) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_RandomAccessIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
__partial_sort(__first, __middle, __last, __VALUE_TYPE(__first), __comp);
}
//partial_sort_copy与partial_sort的实现机制是相同，只是partial_sort_copy将元素排序后放在以result起始的容器中
template
_RandomAccessIter __partial_sort_copy(_InputIter __first,
_InputIter __last,
_RandomAccessIter __result_first,
_RandomAccessIter __result_last,
_Distance*, _Tp*) {
if (__result_first == __result_last) return __result_last;
_RandomAccessIter __result_real_last = __result_first;
while(__first != __last && __result_real_last != __result_last) {
*__result_real_last = *__first;
++__result_real_last;
++__first;
}
make_heap(__result_first, __result_real_last);
while (__first != __last) {
if (*__first < *__result_first)
__adjust_heap(__result_first, _Distance(0),
_Distance(__result_real_last - __result_first),
_Tp(*__first));
++__first;
}
sort_heap(__result_first, __result_real_last);
return __result_real_last;
}
template
inline _RandomAccessIter
partial_sort_copy(_InputIter __first, _InputIter __last,
_RandomAccessIter __result_first,
_RandomAccessIter __result_last) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_CONVERTIBLE(typename iterator_traits<_InputIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
__STL_REQUIRES(typename iterator_traits<_RandomAccessIter>::value_type,
_LessThanComparable);
__STL_REQUIRES(typename iterator_traits<_InputIter>::value_type,
_LessThanComparable);
return __partial_sort_copy(__first, __last, __result_first, __result_last,
__DISTANCE_TYPE(__result_first),
__VALUE_TYPE(__first));
}
template
_RandomAccessIter __partial_sort_copy(_InputIter __first,
_InputIter __last,
_RandomAccessIter __result_first,
_RandomAccessIter __result_last,
_Compare __comp, _Distance*, _Tp*) {
if (__result_first == __result_last) return __result_last;
_RandomAccessIter __result_real_last = __result_first;
while(__first != __last && __result_real_last != __result_last) {
*__result_real_last = *__first;
++__result_real_last;
++__first;
}
make_heap(__result_first, __result_real_last, __comp);
while (__first != __last) {
if (__comp(*__first, *__result_first))
__adjust_heap(__result_first, _Distance(0),
_Distance(__result_real_last - __result_first),
_Tp(*__first),
__comp);
++__first;
}
sort_heap(__result_first, __result_real_last, __comp);
return __result_real_last;
}
template
inline _RandomAccessIter
partial_sort_copy(_InputIter __first, _InputIter __last,
_RandomAccessIter __result_first,
_RandomAccessIter __result_last, _Compare __comp) {
__STL_REQUIRES(_InputIter, _InputIterator);
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_CONVERTIBLE(typename iterator_traits<_InputIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_RandomAccessIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
return __partial_sort_copy(__first, __last, __result_first, __result_last,
__comp,
__DISTANCE_TYPE(__result_first),
__VALUE_TYPE(__first));
}
// nth_element() and its auxiliary functions.
//nth_element版本一辅助函数
template
void __nth_element(_RandomAccessIter __first, _RandomAccessIter __nth,
_RandomAccessIter __last, _Tp*) {
while (__last - __first > 3) {//区间长度大于3
//获取分割点cut
_RandomAccessIter __cut =
__unguarded_partition(__first, __last,
_Tp(__median(*__first,
*(__first + (__last - __first)/2),
*(__last - 1))));
if (__cut <= __nth)//若分割点小于指定位置，则nth位置在右半段
__first = __cut;//再对右半段进行分割
else //否则，对左半段进行分割
__last = __cut;
}
__insertion_sort(__first, __last);
}
//重新排序序列[first,last)，使迭代器nth所指的元素，与“整个[first,last)序列完整排序后，同一位置的元素”同值.
//此外，必须保证[nth,last)内的所有元素不小于[first,nth)内的元素，但是对于序列[first,nth)和序列[nth,last)内的元素的排序顺序不能确定.
/*
函数功能：Rearranges the elements in the range [first,last),
in such a way that the element at the nth position is the element that would be in that position in a sorted sequence.
函数原型：
default (1)
template
void nth_element (RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last);
custom (2)
template
void nth_element (RandomAccessIterator first, RandomAccessIterator nth,
RandomAccessIterator last, Compare comp);
*/
//nth_element版本一
template
inline void nth_element(_RandomAccessIter __first, _RandomAccessIter __nth,
_RandomAccessIter __last) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_REQUIRES(typename iterator_traits<_RandomAccessIter>::value_type,
_LessThanComparable);
__nth_element(__first, __nth, __last, __VALUE_TYPE(__first));
}
template
void __nth_element(_RandomAccessIter __first, _RandomAccessIter __nth,
_RandomAccessIter __last, _Tp*, _Compare __comp) {
while (__last - __first > 3) {
_RandomAccessIter __cut =
__unguarded_partition(__first, __last,
_Tp(__median(*__first,
*(__first + (__last - __first)/2),
*(__last - 1),
__comp)),
__comp);
if (__cut <= __nth)
__first = __cut;
else
__last = __cut;
}
__insertion_sort(__first, __last, __comp);
}
template
inline void nth_element(_RandomAccessIter __first, _RandomAccessIter __nth,
_RandomAccessIter __last, _Compare __comp) {
__STL_REQUIRES(_RandomAccessIter, _Mutable_RandomAccessIterator);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_RandomAccessIter>::value_type,
typename iterator_traits<_RandomAccessIter>::value_type);
__nth_element(__first, __nth, __last, __VALUE_TYPE(__first), __comp);
}
// Binary search (lower_bound, upper_bound, equal_range, binary_search).
template
_ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);//求取整个区间的长度len
_Distance __half;
_ForwardIter __middle;//定义区间的中间迭代器
while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
__half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
__middle = __first;//middle初始化为区间的起始位置
advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
if (*__middle < __val) {//将value值与中间值比较，即是二分查找,若中间值小于value，则继续查找右半部分
//下面两行令first指向middle的下一个位置
__first = __middle;
++__first;
__len = __len - __half - 1;//调整查找区间的长度
}
else
__len = __half;//否则查找左半部分
}
return __first;
}
//在已排序区间[first,last)查找value值
//若该区间存在与value相等的元素，则返回指向第一个与value相等的迭代器
//若该区间不存在与value相等的元素，则返回指向第一个不小于value值的迭代器
//若该区间的任何元素都比value值小，则返回last
/*
函数功能：Returns an iterator pointing to the first element in the range [first,last) which does not compare less than val.
函数原型：
default (1) ：版本一采用operator<比较
template
ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
const T& val);
custom (2) ：版本二采用仿函数comp比较规则
template
ForwardIterator lower_bound (ForwardIterator first, ForwardIterator last,
const T& val, Compare comp);
*/
//版本一
template
inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_REQUIRES(_Tp, _LessThanComparable);
return __lower_bound(__first, __last, __val,
__DISTANCE_TYPE(__first));
}
template
_ForwardIter __lower_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Compare __comp, _Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);//求取整个区间的长度len
_Distance __half;
_ForwardIter __middle;//定义区间的中间迭代器
while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
__half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
__middle = __first;//middle初始化为区间的起始位置
advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
if (__comp(*__middle, __val)) {//若comp判断为true，则继续在右半部分查找
//下面两行令first指向middle的下一个位置
__first = __middle;
++__first;
__len = __len - __half - 1;//调整查找区间的长度
}
else
__len = __half;//否则查找左半部分
}
return __first;
}
//版本二：
template
inline _ForwardIter lower_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Compare __comp) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
return __lower_bound(__first, __last, __val, __comp,
__DISTANCE_TYPE(__first));
}
template
_ForwardIter __upper_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);//求取整个区间的长度len
_Distance __half;
_ForwardIter __middle;//定义区间的中间迭代器
while (__len > 0) {//若区间不为空，则在区间[first,last)开始查找value值
__half = __len >> 1;//向右移一位，相当于除以2，即取区间的中间值
__middle = __first;//middle初始化为区间的起始位置
advance(__middle, __half);//middle向后移half位，此时middle为区间的中间值
if (__val < *__middle)//若value小于中间元素值
__len = __half;//查找左半部分
else {
//下面两行令first指向middle的下一个位置
__first = __middle;
++__first;
__len = __len - __half - 1;//更新len的值
}
}
return __first;
}
//在已排序区间[first,last)查找value值
//返回大于value值的第一个元素的迭代器
/*
函数功能：Returns an iterator pointing to the first element in the range [first,last) which compares greater than val.
函数原型：
default (1) ：版本一采用operator<比较
template
ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
const T& val);
custom (2) ：版本二采用仿函数comp比较规则
template
ForwardIterator upper_bound (ForwardIterator first, ForwardIterator last,
const T& val, Compare comp);
*/
//版本一
template
inline _ForwardIter upper_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_REQUIRES(_Tp, _LessThanComparable);
return __upper_bound(__first, __last, __val,
__DISTANCE_TYPE(__first));
}
template
_ForwardIter __upper_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Compare __comp, _Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);
_Distance __half;
_ForwardIter __middle;
while (__len > 0) {
__half = __len >> 1;
__middle = __first;
advance(__middle, __half);
if (__comp(__val, *__middle))
__len = __half;
else {
__first = __middle;
++__first;
__len = __len - __half - 1;
}
}
return __first;
}
//版本二
template
inline _ForwardIter upper_bound(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val, _Compare __comp) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
return __upper_bound(__first, __last, __val, __comp,
__DISTANCE_TYPE(__first));
}
//函数举例
/*
#include // std::cout
#include // std::lower_bound, std::upper_bound, std::sort
#include // std::vector
int main () {
int myints[] = {10,20,30,30,20,10,10,20};
std::vector v(myints,myints+8); // 10 20 30 30 20 10 10 20
std::sort (v.begin(), v.end()); // 10 10 10 20 20 20 30 30
std::vector::iterator low,up;
low=std::lower_bound (v.begin(), v.end(), 20); // ^
up= std::upper_bound (v.begin(), v.end(), 20); // ^
std::cout << "lower_bound at position " << (low- v.begin()) << '\n';
std::cout << "upper_bound at position " << (up - v.begin()) << '\n';
return 0;
}
Output:
lower_bound at position 3
upper_bound at position 6
*/
template
pair<_ForwardIter, _ForwardIter>
__equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
_Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);//计算区间的长度len
_Distance __half;
_ForwardIter __middle, __left, __right;
while (__len > 0) {//若区间非空
__half = __len >> 1;//len右移一位，相等于除以2，即half为区间的长度的一半
__middle = __first;//初始化middle的值
advance(__middle, __half);//前进middle位置，使其指向区间中间位置
if (*__middle < __val) {//若指定元素value大于中间元素值，则在右半部分继续查找
//下面两行使first指向middle的下一个位置，即右半区间的起始位置
__first = __middle;
++__first;
__len = __len - __half - 1;//更新待查找区间的长度
}
else if (__val < *__middle)//若指定元素value小于中间元素值，则在左半部分继续查找
__len = __half;//更新待查找区间的长度
else {//若指定元素value等于中间元素值
//在前半部分找lower_bound位置
__left = lower_bound(__first, __middle, __val);
advance(__first, __len);
//在后半部分找upper_bound
__right = upper_bound(++__middle, __first, __val);
return pair<_ForwardIter, _ForwardIter>(__left, __right);//返回pair对象，第一个迭代器为left，第二个迭代器为right
}
}
return pair<_ForwardIter, _ForwardIter>(__first, __first);
}
//查找区间与value相等的相邻重复元素的起始位置和结束位置
//注意：[first,last)是已排序，思想还是采用二分查找法
//同样也有两个版本
/*
函数功能：Returns the bounds of the subrange that includes all the elements of the range [first,last) with values equivalent to val.
函数原型：
default (1) ：版本一默认operator<
template
pair
equal_range (ForwardIterator first, ForwardIterator last, const T& val);
custom (2) ：版本二采用仿函数comp
template
pair
equal_range (ForwardIterator first, ForwardIterator last, const T& val,
Compare comp);
*/
//版本一
template
inline pair<_ForwardIter, _ForwardIter>
equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_REQUIRES(_Tp, _LessThanComparable);
return __equal_range(__first, __last, __val,
__DISTANCE_TYPE(__first));
}
template
pair<_ForwardIter, _ForwardIter>
__equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
_Compare __comp, _Distance*)
{
_Distance __len = 0;
distance(__first, __last, __len);
_Distance __half;
_ForwardIter __middle, __left, __right;
while (__len > 0) {
__half = __len >> 1;
__middle = __first;
advance(__middle, __half);
if (__comp(*__middle, __val)) {
__first = __middle;
++__first;
__len = __len - __half - 1;
}
else if (__comp(__val, *__middle))
__len = __half;
else {
__left = lower_bound(__first, __middle, __val, __comp);
advance(__first, __len);
__right = upper_bound(++__middle, __first, __val, __comp);
return pair<_ForwardIter, _ForwardIter>(__left, __right);
}
}
return pair<_ForwardIter, _ForwardIter>(__first, __first);
}
//版本二
template
inline pair<_ForwardIter, _ForwardIter>
equal_range(_ForwardIter __first, _ForwardIter __last, const _Tp& __val,
_Compare __comp) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
return __equal_range(__first, __last, __val, __comp,
__DISTANCE_TYPE(__first));
}
//equal_range函数举例：
/*
#include // std::cout
#include // std::equal_range, std::sort
#include // std::vector
bool mygreater (int i,int j) { return (i>j); }
int main () {
int myints[] = {10,20,30,30,20,10,10,20};
std::vector v(myints,myints+8); // 10 20 30 30 20 10 10 20
std::pair::iterator,std::vector::iterator> bounds;
// using default comparison:
std::sort (v.begin(), v.end()); // 10 10 10 20 20 20 30 30
bounds=std::equal_range (v.begin(), v.end(), 20); // ^ ^
std::cout << "bounds at positions " << (bounds.first - v.begin());
std::cout << " and " << (bounds.second - v.begin()) << '\n';
// using "mygreater" as comp:
std::sort (v.begin(), v.end(), mygreater); // 30 30 20 20 20 10 10 10
bounds=std::equal_range (v.begin(), v.end(), 20, mygreater); // ^ ^
std::cout << "bounds at positions " << (bounds.first - v.begin());
std::cout << " and " << (bounds.second - v.begin()) << '\n';
return 0;
}
Output：
bounds at positions 3 and 6
bounds at positions 2 and 5
*/
//二分查找法
//注意：[first,last)是已排序
//同样也有两个版本
/*
函数功能：Returns true if any element in the range [first,last) is equivalent to val, and false otherwise.
函数原型：
default (1) ：版本一默认operator<
template
bool binary_search (ForwardIterator first, ForwardIterator last,
const T& val);
custom (2) ：版本二采用仿函数comp
template
bool binary_search (ForwardIterator first, ForwardIterator last,
const T& val, Compare comp);
*/
template
bool binary_search(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_REQUIRES(_Tp, _LessThanComparable);
_ForwardIter __i = lower_bound(__first, __last, __val);//调用二分查找函数，并返回不小于value值的第一个迭代器位置i
return __i != __last && !(__val < *__i);
}
template
bool binary_search(_ForwardIter __first, _ForwardIter __last,
const _Tp& __val,
_Compare __comp) {
__STL_REQUIRES(_ForwardIter, _ForwardIterator);
__STL_REQUIRES_SAME_TYPE(_Tp,
typename iterator_traits<_ForwardIter>::value_type);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool, _Tp, _Tp);
_ForwardIter __i = lower_bound(__first, __last, __val, __comp);//调用二分查找函数，并返回不小于value值的第一个迭代器位置i
return __i != __last && !__comp(__val, *__i);
}
// merge, with and without an explicitly supplied comparison function.
//将两个已排序的区间[first1,last1)和区间[first2,last2)合并
/*
函数功能：Combines the elements in the sorted ranges [first1,last1) and [first2,last2),
into a new range beginning at result with all its elements sorted.
函数原型：
default (1) ：版本一
template
OutputIterator merge (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
custom (2) ：版本二
template
OutputIterator merge (InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result, Compare comp);
*/
//版本一：
template
_OutputIter merge(_InputIter1 __first1, _InputIter1 __last1,
_InputIter2 __first2, _InputIter2 __last2,
_OutputIter __result) {
__STL_REQUIRES(_InputIter1, _InputIterator);
__STL_REQUIRES(_InputIter2, _InputIterator);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_REQUIRES_SAME_TYPE(
typename iterator_traits<_InputIter1>::value_type,
typename iterator_traits<_InputIter2>::value_type);
__STL_REQUIRES(typename iterator_traits<_InputIter1>::value_type,
_LessThanComparable);
//两个序列都尚未到达尾端，则执行while循环
/*
情况1：若序列二元素较小,则记录到目标区，且移动序列二的迭代器，但是序列一的迭代器不变.
情况2：若序列一元素较小或相等,则记录到目标区，且移动序列一的迭代器，但是序列二的迭代器不变.
最后：把剩余元素的序列复制到目标区
*/
while (__first1 != __last1 && __first2 != __last2) {
//情况1
if (*__first2 < *__first1) {//若序列二元素较小
*__result = *__first2;//将元素记录到目标区
++__first2;//移动迭代器
}
//情况2
else {//若序列一元素较小或相等
*__result = *__first1;//将元素记录到目标区
++__first1;//移动迭代器
}
++__result;//更新目标区位置，以便下次记录数据
}
//若有序列到达尾端，则把没到达尾端的序列剩余元素复制到目标区
//此时，区间[first1,last1)和区间[first2,last2)至少一个必定为空
return copy(__first2, __last2, copy(__first1, __last1, __result));
}
//版本二
template
_OutputIter merge(_InputIter1 __first1, _InputIter1 __last1,
_InputIter2 __first2, _InputIter2 __last2,
_OutputIter __result, _Compare __comp) {
__STL_REQUIRES(_InputIter1, _InputIterator);
__STL_REQUIRES(_InputIter2, _InputIterator);
__STL_REQUIRES_SAME_TYPE(
typename iterator_traits<_InputIter1>::value_type,
typename iterator_traits<_InputIter2>::value_type);
__STL_REQUIRES(_OutputIter, _OutputIterator);
__STL_BINARY_FUNCTION_CHECK(_Compare, bool,
typename iterator_traits<_InputIter1>::value_type,
typename iterator_traits<_InputIter1>::value_type);
while (__first1 != __last1 && __first2 != __last2) {
if (__comp(*__first2, *__first1)) {
*__result = *__first2;
++__first2;
}
else {
*__result = *__first1;
++__first1;
}
++__result;
}
return copy(__first2, __last2, copy(__first1, __last1, __result));
}
//merge函数举例：
/*
#include // std::cout
#include // std::merge, std::sort
#include // std::vector
int main () {
int first[] = {5,10,15,20,25};
int second[] = {50,40,30,20,10};
std::vector v(10);
std::sort (first,first+5);
std::sort (second,second+5);
std::merge (first,first+5,second,second+5,v.begin());
std::cout << "The resulting vector contains:";
for (std::vector::iterator it=v.begin(); it!=v.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
Output:
The resulting vector contains: 5 10 10 15 20 20 25 30 40 50
*/
// inplace_merge and its auxiliary functions.
//版本一的辅助函数，无缓冲区的操作
template
void __merge_without_buffer(_BidirectionalIter __first,
_BidirectionalIter __middle,
_BidirectionalIter __last,
_Distance __len1, _Distance __len2) {
if (__len1 == 0 || __len2 == 0)
return;
if (__len1 + __len2 == 2) {
if (*__middle < *__first)
iter_swap(__first, __middle);
return;
}
_BidirectionalIter __first_cut = __first;
_BidirectionalIter __second_cut = __middle;
_Distance __len11 = 0;
_Distance __len22 = 0;
if (__len1 > __len2) {
__len11 = __len1 / 2;
advance(__first_cut, __len11);
__second_cut = lower_bound(__middle, __last, *__first_cut);
distance(__middle, __second_cut, __len22);
}
else {
__len22 = __len2 / 2;
advance(__second_cut, __len22);
__first_cut = upper_bound(__first, __middle, *__second_cut);
distance(__first, __first_cut, __len11);
}
_BidirectionalIter __new_middle
= rotate(__first_cut, __middle, __second_cut);
__merge_without_buffer(__first, __first_cut, __new_middle,
__len11, __len22);
__merge_without_buffer(__new_middle, __second_cut, __last, __len1 - __len11,
__len2 - __len22);
}
template
void __merge_without_buffer(_BidirectionalIter __first,
_BidirectionalIter __middle,
_BidirectionalIter __last,
_Distance __len1, _Distance __len2,
_Compare __comp) {
if (__len1 == 0 || __len2 == 0)
return;
if (__len1 + __len2 == 2) {
if (__comp(*__middle, *__first))
iter_swap(__first, __middle);
return;
}
_BidirectionalIter __first_cut = __first;
_BidirectionalIter __second_cut = __middle;
_Distance __len11 = 0;
_Distance __len22 = 0;
if (__len1 > __len2) {
__len11 = __len1 / 2;
advance(__first_cut, __len11);
__second_cut = lower_bound(__middle, __last, *__first_cut, __comp);
distance(__middle, __second_cut, __len22);
}
else {
__len22 = __len2 / 2;
advance(__second_cut, __len22);
__first_cut = upper_bound(__first, __middle, *__second_cut, __comp);
distance(__first, __first_cut, __len11);
}
_BidirectionalIter __new_middle
= rotate(__first_cut, __middle, __second_cut);
__merge_without_buffer(__first, __first_cut, __new_middle, __len11, __len22,
__comp);
__merge_without_buffer(__new_middle, __second_cut, __last, __len1 - __len11,
__len2 - __len22, __comp);
}
//版本一的辅助函数，有缓冲区的操作
template