map大小和互换
功能描述：
统计map容器大小以及交换map容器

函数原型：

代码如下：

#include <iostream>
using namespace std;
#include <map>//map容器  大小和交换
void test01() {map<int, int>m;m.insert(pair<int, int>(1, 10));m.insert(pair<int, int>(2, 20));m.insert(pair<int, int>(3, 30));if (m.empty()) {cout << "m为空" << endl;} else {cout << "m不为空" << endl;cout << "m的大小为：" << m.size() << endl;}
}void printMap(map<int, int> &m) {for (map<int, int>::iterator it = m.begin(); it != m.end(); it++) {cout << "key = " << it->first << " " << "value = " << it->second << endl;}cout << endl;
}void test02() {map<int, int>m1;m1.insert(pair<int, int>(1, 10));m1.insert(pair<int, int>(2, 20));m1.insert(pair<int, int>(3, 30));map<int, int>m2;m2.insert(pair<int, int>(4, 100));m2.insert(pair<int, int>(5, 200));m2.insert(pair<int, int>(6, 300));cout << "交换前：" << endl;printMap(m1);printMap(m2);cout << "交换后：" << endl;m1.swap(m2);printMap(m1);printMap(m2);}int main() {test01();cout << "----------------------" << endl;test02();return 0;
}