19.允许重复的unordered_map

 #include <string>
 #include <iostream>
 //查询性能最高
 //允许重复的,hash_map
 #include <unordered_map>
 #include <algorithm>
 using namespace std;

 void main()
 {
     //允许重复的映射
     unordered_multimap<string, double>mymap{ {"a1",},{ "a2", },{ "a3", } };

     mymap.insert(pair<string, double>("a4", ));
     mymap.insert(pair<string, double>("a4", ));
     mymap.insert(pair<string, double>("a4", ));
     mymap.insert(pair<string, double>("a4", ));

     /*mymap.insert(unordered_multimap<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;
     }*/

     //查找所有
     auto it = mymap.equal_range("a4");

     for_each(it.first, it.second, [](unordered_multimap<string, double>::value_type &x) {cout << x.first << "  " << x.second << endl; });
     cin.get();
 }