c++中map按key和value排序

```
#include<iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
using namespace std;

/*按key升序*/
void test01(){
    map<string,int,less<string> > map1;
    map1.insert(pair<string,int>("aba",3));
    map1.insert(pair<string,int>("aaa",2));
    map1.insert(pair<string,int>("ddd",1));
    map1.insert(pair<string,int>("ccc",4));

    for(map<string,int>::iterator it=map1.begin(); it!=map1.end(); it++ ){
        cout<<(*it).first<<" : "<<(*it).second<<endl;
    }
}
/*按key降序*/
void test02(){
    map<string,int,greater<string> > map1;
    map1.insert(pair<string,int>("aba",3));
    map1.insert(pair<string,int>("aaa",2));
    map1.insert(pair<string,int>("ddd",1));
    map1.insert(pair<string,int>("ccc",4));

    for(map<string,int>::iterator it=map1.begin(); it!=map1.end(); it++ ){
        cout<<(*it).first<<" : "<<(*it).second<<endl;
    }
}
/*----------------------------------------------------*/
/*编写类或者结构体按key升序或者降序*/
class flag{
public:
    bool operator()(string v1,string v2){
        return v1<v2;
    }
};

void test03(){
    map<string,int,flag> map1;
    map1.insert(pair<string,int>("aba",3));
    map1.insert(pair<string,int>("aaa",2));
    map1.insert(pair<string,int>("ddd",1));
    map1.insert(pair<string,int>("ccc",4));

    for(map<string,int>::iterator it=map1.begin(); it!=map1.end(); it++ ){
        cout<<(*it).first<<" : "<<(*it).second<<endl;
    }
}
/*-------------------------------------------------------*/
/*自定义编写类或者函数或者结构体进行值排序*/
/*自定义函数编写不用()，自定义类或者结构体需要()*/
bool flag_2(pair<string,int> o1,pair<string,int> o2){
    return o1.second>o2.second;
}
class flag_2{
public:
    bool operator()(pair<string,int> o1,pair<string,int> o2){
        return o1.second>o2.second;
    }
};
struct flag_2{
    bool operator()(pair<string,int> o1,pair<string,int> o2){
        return o1.second<o2.second;
    }
};
void test04(){
    map<string,int> map1;
    map1.insert(pair<string,int>("aba",3));
    map1.insert(pair<string,int>("aaa",2));
    map1.insert(pair<string,int>("ddd",1));
    map1.insert(pair<string,int>("ccc",4));
    
    //利用vector进行value排序
    vector< pair<string,int> > dic1(map1.begin(),map1.end());
    sort(dic1.begin(),dic1.end(),flag_2());

    for(int i=0; i<dic1.size(); i++ ){
        cout<<dic1[i].first<<" "<<dic1[i].second<<endl;
    }
}
int main(){
    //test01();
    //test02();
    //test03();
    test04();

    return 0;
}

```