C++ unordered_map用法

1.声明
2.初始化
3.遍历
4.插入
5.查找

示例

#include<string> 
#include<iostream> 
#include<unordered_map>
using namespace std; 
   
int main()
{
    unordered_map<string, int>  dict; // 声明unordered_map对象
     
    // 插入数据的三种方式
    dict.insert(pair<string,int>("apple",2));
    dict.insert(unordered_map<string, int>::value_type("orange",3));
    dict["banana"] = 6;
     
    //删除，如果没找到也不会出错
    dict.erase("pear");
    // 判断是否有元素
    if(dict.empty())
        cout<<"该字典无元素"<<endl;
    else
        cout<<"该字典共有"<<dict.size()<<"个元素"<<endl;
     
    // 遍历
    unordered_map<string, int>::iterator iter;
    for(iter=dict.begin();iter!=dict.end();iter++)
        cout<<iter->first<<ends<<iter->second<<endl;
     
    // 查找
    if(dict.count("boluo")==0)
        cout<<"can't find boluo!"<<endl;
    else
        cout<<"find boluo!"<<endl;
     
    if((iter=dict.find("banana"))!=dict.end())
        cout<<"banana="<<iter->second<<endl;
    else
        cout<<"can't find boluo!"<<endl;
     
    return 0;
}