C/C++编程：STL list的使用
概述
- list<>由双向链表实现而成。这意味着list内的每个元素都以一部分内存指示其前导元素和后继元素
- list<>不提供随机访问，因此如果你要访问第10个元素，必须沿着链表依次走过前9个元素
- list<>的优势是：在任何位置上执行安插或者删除动作都非常快速，因为只需要改变链接就好
构造函数&&析构函数
非更易型操作
赋值操作
元素访问
迭代器
插入&&删除
Splice(接和)函数以及会改变元素次序的函数
异常处理
实例
构造
#include
#include
#include
template
std::ostream& operator<<(std::ostream& s, const std::list& v)
{
s.put('[');
char comma[3] = {'\0', ' ', '\0'};
for (const auto& e : v) {
s << comma << e;
comma[0] = ',';
}
return s << ']';
}
int main()
{
// C++11 初始化器列表语法：
std::list words1 {"the", "frogurt", "is", "also", "cured"};
std::cout << "words1: " << words1 << '\n';
// words2 == words1
std::list words2(words1.begin(), words1.end());
std::cout << "words2: " << words2 << '\n';
// words3 == words1
std::list words3(words1);
std::cout << "words3: " << words3 << '\n';
// words4 为 {"Mo", "Mo", "Mo", "Mo", "Mo"}
std::list words4(5, "Mo");
std::cout << "words4: " << words4 << '\n';
return 0;
}
std::list::operator=、std::list::assign
- std::list
- std::list
#include
#include
#include
void display_sizes(const std::list& nums1,
const std::list& nums2,
const std::list& nums3)
{
std::cout << "nums1: " << nums1.size()
<< " nums2: " << nums2.size()
<< " nums3: " << nums3.size() << '\n';
}
int main()
{
std::list nums1 {3, 1, 4, 6, 5, 9};
std::list nums2;
std::list nums3;
std::cout << "Initially:\n";
display_sizes(nums1, nums2, nums3);
// 复制赋值从 nums1 复制数据到 nums2
nums2 = nums1;
std::cout << "After assigment:\n";
display_sizes(nums1, nums2, nums3);
// 移动赋值从 nums1 移动数据到 nums3,
// 一同修改 nums1 和 nums3
nums3 = std::move(nums1);
std::cout << "After move assigment:\n";
display_sizes(nums1, nums2, nums3);
return 0;
}
#include
#include
#include
int main()
{
std::list characters;
characters.assign(5, 'a');
for (char c : characters) {
std::cout << c << ' ';
}
characters.assign({'\n', 'C', '+', '+', '1', '1', '\n'});
for (char c : characters) {
std::cout << c;
}
return 0;
}
front、back
-
std::list
front会引发未定义行为 -
std::list
back会引发未定义行为
#include
#include
int main()
{
std::list letters {'o', 'm', 'g', 'w', 't', 'f'};
if (!letters.empty()) {
std::cout << "The first character is: " << letters.front() << '\n';
std::cout << "The last character is: " << letters.back() << '\n';
}
}
begin、end、rbegin、rend
- begin：返回指向list首元素的迭代器
- end： 返回指向
list末元素后一元素的迭代器。
#include
#include
#include
#include
int main()
{
std::list nums {1, 2, 4, 8, 16};
std::list fruits {"orange", "apple", "raspberry"};
std::list empty;
// 求和 list nums 中的所有整数（若存在），仅打印结果。
std::cout << "Sum of nums: " <<
std::accumulate(nums.begin(), nums.end(), 0) << "\n";
// 打印 list fruits 中的首个 fruis
if(!fruits.empty()){
std::cout << "First fruit: " << *fruits.begin() << "\n";
}
if (empty.begin() == empty.end())
std::cout << "list 'empty' is indeed empty.\n";
}
empty、size、max_size、resize
- empty：检查容器是否为空
- size：返回容器中的元素数，相当于 std::distance(begin(), end())
-
max_size：返回最大可以容纳的元素个数
-
resize：重设容器大小以容纳count个元素
#include
#include
int main()
{
std::list numbers;
std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';
numbers.push_back(42);
numbers.push_back(13317);
std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
}
#include
#include
#include
int main()
{
std::list numbers;
std::cout << "max size: " << numbers.max_size() << '\n';
std::cout << "max size: " << std::numeric_limits>::max().max_size()<< '\n';
}
#include
#include
int main()
{
std::list c = {1, 2, 3};
std::cout << "The list holds: ";
for(auto& el: c) std::cout << el << ' ';
std::cout << '\n';
c.resize(5);
std::cout << "After resize up to 5: ";
for(auto& el: c) std::cout << el << ' ';
std::cout << '\n';
c.resize(2);
std::cout << "After resize down to 2: ";
for(auto& el: c) std::cout << el << ' ';
std::cout << '\n';
}
swap
#include
#include
template
Os& operator<<(Os& os, const Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}
int main()
{
std::list a1{1, 2, 3}, a2{4, 5};
auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());
int & ref1 = a1.front();
int & ref2 = a2.front();
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
a1.swap(a2);
std::cout << a1 << a2 << *it1 << ' ' << *it2 << ' ' << ref1 << ' ' << ref2 << '\n';
// 注意交换后迭代器与引用保持与其原来的元素关联，例如指向 'a1' 中值为 2 的元素的 it1 仍指向同一元素，
// 尽管此元素被移动到 'a2' 中。
}
效果
#include
#include
#include
int main()
{
std::list alice{1, 2, 3};
std::list bob{7, 8, 9, 10};
auto print = [](const int& n) { std::cout << " " << n; };
// 打印交换前的状态
std::cout << "alice:";
std::for_each(alice.begin(), alice.end(), print);
std::cout << '\n';
std::cout << "bob :";
std::for_each(bob.begin(), bob.end(), print);
std::cout << '\n';
std::cout << "-- SWAP\n";
std::swap(alice,bob);
// 打印交换后的状态
std::cout << "alice:";
std::for_each(alice.begin(), alice.end(), print);
std::cout << '\n';
std::cout << "bob :";
std::for_each(bob.begin(), bob.end(), print);
std::cout << '\n';
}
效果
clear、erase
- clear：从容器擦除所有元素。此调用后 size() 返回零。
-
erase：从容器擦除指定的元素
- 1) 移除位于
pos的元素。- 2) 移除范围
[first; last)中的元素。
#include
#include
#include
int main()
{
std::list container{1, 2, 3};
auto print = [](const int& n) { std::cout << " " << n; };
std::cout << "Before clear:";
std::for_each(container.begin(), container.end(), print);
std::cout << "\nSize=" << container.size() << '\n';
std::cout << "Clear\n";
container.clear();
std::cout << "After clear:";
std::for_each(container.begin(), container.end(), print);
std::cout << "\nSize=" << container.size() << '\n';
}
#include
#include
#include
int main( )
{
std::list c{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
for (auto &i : c) {
std::cout << i << " ";
}
std::cout << '\n';
c.erase(c.begin());
for (auto &i : c) {
std::cout << i << " ";
}
std::cout << '\n';
std::list::iterator range_begin = c.begin();
std::list::iterator range_end = c.begin();
std::advance(range_begin,2);
std::advance(range_end,5);
c.erase(range_begin, range_end);
for (auto &i : c) {
std::cout << i << " ";
}
std::cout << '\n';
}
#include
#include
#include
void print_container(const std::list& c)
{
for (auto x : c) {
std::cout << x << ' ';
}
std::cout << '\n';
}
int main()
{
std::list cnt(10);
std::iota(cnt.begin(), cnt.end(), '0');
std::cout << "Init:\n";
print_container(cnt);
auto erased = std::erase(cnt, '3');
std::cout << "Erase \'3\':\n";
print_container(cnt);
std::erase_if(cnt, [](char x) { return (x - '0') % 2 == 0; });
std::cout << "Erase all even numbers:\n";
print_container(cnt);
std::cout << "In all " << erased << " even numbers were erased.\n";
}
emplace、emplace_front、push_back
- emplace：直接于pos前插入元素到容器中
- emplace_front、push_front：插入新元素到容器起始
-
emplace_back、push_back：插入新元素到容器末尾
- pop_back：移除容器的末元素。在空容器上调用
pop_back导致未定义行为。指向被擦除元素的迭代器和引用被非法化。
#include
#include
#include
struct A{
std::string s;
A(std::string str) : s(std::move(str)) { std::cout << " constructed\n"; }
A(const A& o) : s(o.s) { std::cout << " copy constructed\n"; }
A(A&& o) : s(std::move(o.s)) { std::cout << " move constructed\n"; }
A& operator=(const A& other) {
s = other.s;
std::cout << " copy assigned\n";
return *this;
}
A& operator=(A&& other) {
s = std::move(other.s);
std::cout << " move assigned\n";
return *this;
}
};
int main()
{
std::list container;
std::cout << "construct 2 times A:\n";
A two { "two" };
A three { "three" };
std::cout << "emplace:\n";
container.emplace(container.end(), "one");
std::cout << "emplace with A&:\n";
container.emplace(container.end(), two);
std::cout << "emplace with A&&:\n";
container.emplace(container.end(), std::move(three));
std::cout << "content:\n";
for (const auto& obj : container)
std::cout << ' ' << obj.s;
std::cout << '\n';
}
#include
#include
template
void print(T const & xs)
{
std::cout << "[ ";
for(auto && x : xs) {
std::cout << x << ' ';
}
std::cout << "]\n";
}
int main()
{
std::list numbers;
print(numbers);
numbers.push_back(5);
numbers.push_back(3);
numbers.push_back(4);
print(numbers);
numbers.pop_back();
print(numbers);
}
merge
-
merge：归并两排序链表为一个
#include
#include
std::ostream& operator<<(std::ostream& ostr, const std::list& list)
{
for (auto &i : list) {
ostr << " " << i;
}
return ostr;
}
int main()
{
std::list list1 = { 5,9,0,1,3 };
std::list list2 = { 8,7,2,6,4 };
list1.sort();
list2.sort();
std::cout << "list1: " << list1 << "\n";
std::cout << "list2: " << list2 << "\n";
list1.merge(list2);
std::cout << "merged: " << list1 << "\n";
}
splice
-
splice：从一个list转移元素给另一个。不复制或者移动元素，仅重指向链表节点的内部指针
#include
#include
std::ostream& operator<<(std::ostream& ostr, const std::list& list)
{
for (auto &i : list) {
ostr << " " << i;
}
return ostr;
}
int main()
{
std::list list1 = { 1, 2, 3, 4, 5 };
std::list list2 = { 10, 20, 30, 40, 50 };
auto it = list1.begin();
std::advance(it, 2);
list1.splice(it, list2);
std::cout << "list1: " << list1 << "\n";
std::cout << "list2: " << list2 << "\n";
list2.splice(list2.begin(), list1, it, list1.end());
std::cout << "list1: " << list1 << "\n";
std::cout << "list2: " << list2 << "\n";
}
remove, remove_if
#include
#include
int main()
{
std::list l = { 1,100,2,3,10,1,11,-1,12 };
l.remove(1); // 移除两个等于 1 的元素
l.remove_if([](int n){ return n > 10; }); // 移除全部大于 10 的元素
for (int n : l) {
std::cout << n << ' ';
}
std::cout << '\n';
}
reverse
- 作用：逆转容器中的元素顺序。不非法化任何引用或迭代器。
#include
#include
std::ostream& operator<<(std::ostream& ostr, const std::list& list)
{
for (auto &i : list) {
ostr << " " << i;
}
return ostr;
}
int main()
{
std::list list = { 8,7,5,9,0,1,3,2,6,4 };
std::cout << "before: " << list << "\n";
list.sort();
std::cout << "ascending: " << list << "\n";
list.reverse();
std::cout << "descending: " << list << "\n";
}
unique
- 从容器移除所有相继的重复元素。只留下相等元素组中的第一个元素。
#include
#include
int main()
{
std::list x = {1, 2, 2, 3, 3, 2, 1, 1, 2};
std::cout << "contents before:";
for (auto val : x)
std::cout << ' ' << val;
std::cout << '\n';
x.unique();
std::cout << "contents after unique():";
for (auto val : x)
std::cout << ' ' << val;
std::cout << '\n';
return 0;
}
比较
#include
#include
int main()
{
std::list alice{1, 2, 3};
std::list bob{7, 8, 9, 10};
std::list eve{1, 2, 3};
std::cout << std::boolalpha;
// 比较不相等的容器
std::cout << "alice == bob returns " << (alice == bob) << '\n';
std::cout << "alice != bob returns " << (alice != bob) << '\n';
std::cout << "alice < bob returns " << (alice < bob) << '\n';
std::cout << "alice <= bob returns " << (alice <= bob) << '\n';
std::cout << "alice > bob returns " << (alice > bob) << '\n';
std::cout << "alice >= bob returns " << (alice >= bob) << '\n';
std::cout << '\n';
// 比较相等的容器
std::cout << "alice == eve returns " << (alice == eve) << '\n';
std::cout << "alice != eve returns " << (alice != eve) << '\n';
std::cout << "alice < eve returns " << (alice < eve) << '\n';
std::cout << "alice <= eve returns " << (alice <= eve) << '\n';
std::cout << "alice > eve returns " << (alice > eve) << '\n';
std::cout << "alice >= eve returns " << (alice >= eve) << '\n';
}
如果想要扩展list的功能
看个例子：
#include
#include
template
class List : public std::list {
public:
template
List(ARGS &&...args) : std::list(std::forward(args)...) {};
~List() = default;
void append(List &other) {
if (other.empty()) {
return;
}
this->insert(this->end(), other.begin(), other.end());
other.clear();
}
template
void for_each(FUNC &&func) {
for (auto &t : *this) {
func(t);
}
}
template
void for_each(FUNC &&func) const {
for (auto &t : *this) {
func(t);
}
}
};