C++ multimap 用法总结例子

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软件工程小施同学 2022-04-27 21:26:36 博主文章分类：C++

文章标签 C++ #include 一对多 i++ 文章分类 C/C++ 后端开发

#include <map>  
#include <string>  
#include <iostream>  
using namespace std;  
  
int main()  
{  
    ///1. 初始化  
    multimap<int, string, greater<int>> mapStudent;  
    multimap<int, string>::iterator iter, beg, end;  
      
    ///2. 添加元素  
    ///multimap不支持下标操作  
    mapStudent.insert(pair<int, string>(0, "student_one_1"));  
    mapStudent.insert(pair<int, string>(0, "student_one_2"));///一对多 
    mapStudent.insert(pair<int, string>(0, "student_one_3"));///一对多
    mapStudent.insert(pair<int, string>(1, "student_two"));  
    mapStudent.insert(pair<int, string>(5, "Fear Kubrick"));  
    mapStudent.insert(pair<int, string>(2, "Akemi Homura"));  
    mapStudent.insert(pair<int, string>(-1, "Eren Jaeger"));  
    mapStudent.insert(pair<int, string>(99, "lin"));  
    cout << "总数：" << mapStudent.size() << endl;  
    cout << endl;  
      
    ///3. 遍历  
    for (iter = mapStudent.begin(); iter != mapStudent.end(); iter++)  
        cout << iter->first << " " << iter->second << endl;  
    cout << endl;  
      
    ///4. 单键查询与范围查询  
    ///单键查询  
    int count = mapStudent.count(0);  
    iter = mapStudent.find(0);  
    for (int i = 0; i < count; i++, iter++)  
        cout << iter->first << " " << iter->second << endl;  
    cout << endl;  

      
    ///5. 删除  
    iter = mapStudent.find(1);  
    mapStudent.erase(iter);  
    cout << "总数：" << mapStudent.size() << endl;  
    for (iter = mapStudent.begin(); iter != mapStudent.end(); iter++)  
        cout << iter->first << " " << iter->second << endl;  
    cout << endl;  
    
    ///6. 删除多个相同key中的特定一个
    int count2 = mapStudent.count(0);  
    iter = mapStudent.find(0);  
    for (int i = 0; i < count2; i++, iter++){
        if(iter->first == 0 && iter->second == "student_one_2"){
            mapStudent.erase(iter);
        }
    }
     
    cout << "总数：" << mapStudent.size() << endl;  
    for (iter = mapStudent.begin(); iter != mapStudent.end(); iter++)  
        cout << iter->first << " " << iter->second << endl;  
    cout << endl;  
    
    
      
    ///7. 判空与清空  
    if (!mapStudent.empty()){
        mapStudent.clear();  
    }
    
}