18.查询效率最高的unordered_map

#include <string>
#include <iostream>
//查询性能最高
//增删查改与map是一样的,但是本质区别就是unordered_map底层是hash表,map底层是红黑树
#include <unordered_map>
using namespace std;


void main()
{
    unordered_map<string, double>mymap{ {"a1",113},{ "a2",143 },{ "a3",1123 } };

    //不允许重复
    mymap.insert(pair<string, double>("a4", 345));

    mymap.insert(unordered_map<string, double>::value_type("a5", 3425));

    for (auto i : mymap)
    {
        cout << i.first << "  " << i.second << endl;
    }

    auto it = mymap.find("a1");
    if (it != mymap.end())
    {
        cout << it->second << endl;
    }
    cin.get();
}