pair的动态数组排序

1.pair在头文件utility中，可以有pair定义动态数组进行排序，pair中内置了<的默认排序方式，即对first进行默认的升序排序，也可以通过sort函数自定义排序方式

 pair的vector类型

bool strict_weak_ordering(const std::pair<int,std::string>a,const std::pair<int,std::string>b)   

  {   return   a.first   <   b.first;   }   

  int   main()   

  {   

        using   namespace   std;   

        vector<pair<int,   string>   >   vec;   

        vec.push_back(make_pair<int,   string>(5,   "hello"));   

        vec.push_back(make_pair<int,   string>(4,   "hell"));   

        vec.push_back(make_pair<int,   string>(6,   "hello,"));   

        sort(vec.begin(),   vec.end(),   strict_weak_ordering); 

        vector<pair<int,   string>   >::iterator   it   =   vec.begin(),   end   =   vec.end();   

        for(;it   !=   end;   ++it)   

              cout<<it->second<<endl;   

  }

pair的基础操作 https://blog.csdn.net/sunpeishuai/article/details/81239123

#include <utility>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
 
typedef pair<int, int> P;
 
const int N = 5;
pair<int, int> items[N];
 
bool cmp(const P &a, const P&b)
{
    if (a.first < b.first)
        return true;
    else return false;
}
 
int main()
{
    srand(time(NULL));
 
    for (int i = 0; i < N; i++)
        items[i] = make_pair(rand(), i + 1);
 
    cout << "before sorted:" << endl;
    for (int i = 0; i < N; i++)
        cout << "(" << items[i].first << ", " << items[i].second << ")\t";
    cout << endl;
 
    sort(items, items + N, cmp);
 
    cout << "\nafter sorted:" << endl;
    for (int i = 0; i < N; i++)
        cout << "(" << items[i].first << ", " << items[i].second << ")\t";
    cout << endl;
 
    cin.get();
    return 0;
}