STL：set/multiset用法详解

转自：http://blog.csdn.net/ctthuangcheng/article/details/9232725

集合

使用set或multiset之前，必须加入头文件<set>

Set、multiset都是集合类，差别在与set中不允许有重复元素，multiset中允许有重复元素。

sets和multiset内部以平衡二叉树实现

1.   常用函数

1)        构造函数和析构函数

set c:创建空集合,不包含任何元素

set c(op):以op为排序准则，产生一个空的set

set c1(c2):复制c2中的元素到c1中

set c(const value_type *first, const value_type* last):复制[first, last)之间元素构成新集合

set c(const value_type *first, const value_type* last,op):以op为排序准则，复制[first, last)之间元素构成新集合。

c.~set()销毁所有元素，释放内存

multiset mc:创建空集合,不包含任何元素

multiset mc(op):以op为排序准则，产生一个空的set

multiset c1(c2):复制c2中的元素到c1中

multiset c(const value_type *first, const value_type* last):复制[first, last)之间元素构成新集合

multiset c(const value_type *first, const value_type* last,op):以op为排序准则，复制[first, last)之间元素构成新集合。

c.~set()销毁所有元素，释放内存

 // constructing sets
 #include <iostream>
 #include <set>

 bool fncomp (int lhs, int rhs) {return lhs<rhs;}

 struct classcomp {
   bool operator() (const int& lhs, const int& rhs) const
   {return lhs<rhs;}
 };

 int main ()
 {
   std::set<int> first;                           // empty set of ints

   int myints[]= {10,20,30,40,50};
   std::set<int> second (myints,myints+5);        // range

   std::set<int> third (second);                  // a copy of second

   std::set<int> fourth (second.begin(), second.end());  // iterator ctor.

   std::set<int,classcomp> fifth;                 // class as Compare

   bool(*fn_pt)(int,int) = fncomp;
   std::set<int,bool(*)(int,int)> sixth (fn_pt);  // function pointer as Compare

   return 0;
 }

2)        大小、判断空函数

    int size() const:返回容器元素个数
    bool empty() const:判断容器是否为空，若返回true，表明容器已空

3)        增加、删除函数

      pair<iterator,bool> insert( x):插入元素x

    iterator insert(iterator it,x):在迭代器it处插入元素x

    void insert(const value_type *first,const value_type *last):插入[first, last)之间元素

    iterator erase(iterator it):删除迭代器指针it处元素

    iterator erase(iterator first,iterator last):删除[first, last)之间元素

    size_type erase(const Key& key):删除元素值等于key的元素

 #include <iostream>
 #include <set>

 int main ()
 {
   std::set<int> myset;
   std::set<int>::iterator it;
   std::pair<std::set<int>::iterator,bool> ret;

   // set some initial values:
   for (int i=1; i<=5; ++i) myset.insert(i*10);    // set: 10 20 30 40 50

   ret = myset.insert(20);               // no new element inserted

   if (ret.second==false) it=ret.first;  // "it" now points to element 20

   myset.insert (it,25);                 // max efficiency inserting
   myset.insert (it,24);                 // max efficiency inserting
   myset.insert (it,26);                 // no max efficiency inserting

   int myints[]= {5,10,15};              // 10 already in set, not inserted
   myset.insert (myints,myints+3);

   std::cout << "myset contains:";
   for (it=myset.begin(); it!=myset.end(); ++it)
     std::cout << ' ' << *it;
   std::cout << '\n';

   return 0;
 }

 #include <iostream>
 #include <set>

 int main ()
 {
   std::set<int> myset;
   std::set<int>::iterator it;

   // insert some values:
   for (int i=1; i<10; i++) myset.insert(i*10);  // 10 20 30 40 50 60 70 80 90

   it = myset.begin();
   ++it;                                         // "it" points now to 20

   myset.erase (it);

   myset.erase (40);

   it = myset.find (60);
   myset.erase (it, myset.end());

   std::cout << "myset contains:";
   for (it=myset.begin(); it!=myset.end(); ++it)
     std::cout << ' ' << *it;
   std::cout << '\n';

   return 0;
 }

4)        遍历函数

     iterator begin():返回首元素的迭代器指针

    iterator end()：返回尾元素的迭代器指针
    reverse_iterator rbegin():返回尾元素的逆向迭代器指针
    reverse_iterator rend():返回首元素前一个位置的迭代器指针

     

 #include <iostream>
 #include <set>

 int main ()
 {
   int myints[] = {75,23,65,42,13};
   std::set<int> myset (myints,myints+5);

   std::cout << "myset contains:";
   for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
     std::cout << ' ' << *it;

   std::cout << '\n';

   return 0;
 }

5)        操作函数

       const_iterator lower_bound(const Key& key):返回容器中大于等于key的迭代器指针

    const_iterator upper_bound(const Key& key):返回容器中大于key的迭代器指针

    int count(const Key& key) const:返回容器中元素等于key的元素的个数
    pair<const_iterator,const_iterator> equal_range(const Key& key) const:返回容器中元素值等于key的迭代指针[first, last)
    const_iterator find(const Key& key) const:查找功能，返回元素值等于key的迭代器指针
    void swap(set& s):交换集合元素
    void swap(multiset& s):交换多集合元素  

 #include <iostream>
 #include <set>

 int main ()
 {
   std::set<int> myset;
   std::set<int>::iterator itlow,itup;

   for (int i=1; i<10; i++) myset.insert(i*10); // 10 20 30 40 50 60 70 80 90

   itlow=myset.lower_bound (30);                //       ^
   itup=myset.upper_bound (60);                 //                   ^

   myset.erase(itlow,itup);                     // 10 20 70 80 90

   std::cout << "myset contains:";
   for (std::set<int>::iterator it=myset.begin(); it!=myset.end(); ++it)
     std::cout << ' ' << *it;
   std::cout << '\n';

   return 0;
 }

 #include "stdafx.h"
 #include <iostream>
 #include <set>

 using namespace std;

 int main ()
 {
     set<int> myset;

     for (int i=1; i<=5; i++) myset.insert(i*10);   // myset: 10 20 30 40 50

     pair<set<int>::const_iterator,set<int>::const_iterator> ret;
     ret = myset.equal_range(30);

     cout << "the lower bound points to: " << *ret.first << '\n';
     cout << "the upper bound points to: " << *ret.second << '\n';

     return 0;
 }

 #include "stdafx.h"
 #include <iostream>
 #include <set>

 using namespace std;

 int main ()
 {
     int myints[]={12,75,10,32,20,25};
     set<int> first (myints,myints+3);     // 10,12,75
     set<int> second (myints+3,myints+6);  // 20,25,32

     first.swap(second);

     cout << "first contains:";
     for (set<int>::iterator it=first.begin(); it!=first.end(); ++it)
         cout << ' ' << *it;
     cout << '\n';

     cout << "second contains:";
     for (set<int>::iterator it=second.begin(); it!=second.end(); ++it)
         cout << ' ' << *it;
     cout << '\n';

     return 0;
 }