用哈希表标记涂过的矩形，c++中的map

#include<iostream>
#include<vector>
#include<map>
#include<algorithm>

using namespace std;

int main(){
    int n;
    cin >> n;
    int max_y = 0;
    int max_x = 0;
    map<pair<int,int>,int> mp;
    int cnt = 0;
    for(int i = 0;i < n;i++)
    {
        int x1,x2,y1,y2;
        cin >> x1 >> y1 >> x2 >> y2;
        max_x = max(max_x,x2);
        max_x = max(max_x,x1);
        max_y = max(max_y,y1);
        max_y = max(max_y,y2);
        for(int x = x1;x < x2;x++)
        {
            for(int j = y1; j < y2;j++)
            {
                mp[{x,j}] = 1;
            }
        }

    }

    for(auto [x,y]:mp)
    {
        if(y == 1)
        cnt++;
    }

    cout << cnt << endl;


    return 0;
}