STLset container size and swap

STLset container size and swap

Function description:
Count the size of set container and exchange set container
Function prototype:

size();        //返回容器中元素的数目
empty();      //判断容器是否为空
swap(st);     //交换两个集合容器

Code example:

#include<iostream>
#include<set>
using namespace std;
void printSet(set<int>&s)
{
    
    
       for (set<int>::iterator it = s.begin(); it != s.end(); it++)
       {
    
    
              cout << *it << " ";
       }
       cout << endl;
}
void test01()
{
    
    
       set<int>s1;
       //插入数据
       s1.insert(10);
       s1.insert(20);
       s1.insert(30);
       s1.insert(40);
       //打印容器
       printSet(s1);
       //判断是否为空
       if (s1.empty())
       {
    
    
              cout << "s1为空" << endl;
       }
       else
       {
    
    
              cout << "s1不为空" << endl;
              cout << "s1的大小为：" << s1.size() << endl;
       }
}
void test02()
{
    
    
       set<int>s1;
       //插入数据
       s1.insert(10);
       s1.insert(20);
       s1.insert(30);
       s1.insert(40);
       set<int>s2;
       //插入数据
       s2.insert(100);
       s2.insert(200);
       s2.insert(300);
       s2.insert(400);
       cout << "交换前：" << endl;
       printSet(s1);
       printSet(s2);
       cout << "交换后：" << endl;
       s1.swap(s2);
       printSet(s1);
       printSet(s2);
}
int main()
{
    
    
       test01();
       test02();
       return 0;
}

to sum up:

Statistical size—size to
determine whether it is empty—empty
exchange container—swap