c 2b 2b sort map by value

1#include <iostream>
2#include <map>
3#include <vector>
4#include <algorithm>
5 
6typedef std::pair<std::string, int> pair;
7 
8int main()
9{
10    // input map
11    std::map<std::string, int> map = {
12        {"two", 2}, {"one", 1}, {"four", 4}, {"three", 3}
13    };
14 
15    // create an empty vector of pairs
16    std::vector<pair> vec;
17 
18    // copy key-value pairs from the map to the vector
19    std::copy(map.begin(),
20            map.end(),
21            std::back_inserter<std::vector<pair>>(vec));
22 
23    // sort the vector by increasing the order of its pair's second value
24    // if the second value is equal, order by the pair's first value
25    std::sort(vec.begin(), vec.end(),
26            [](const pair &l, const pair &r)
27            {
28                if (l.second != r.second) {
29                    return l.second < r.second;
30                }
31 
32                return l.first < r.first;
33            });
34 
35    // print the vector
36    for (auto const &pair: vec) {
37        std::cout << '{' << pair.first << "," << pair.second << '}' << std::endl;
38    }
39 
40    return 0;
41}