洛谷 P5542 [USACO19FEB]Painting The Barn

题目传送门

解题思路:

二维差分的板子题.题解传送门

AC代码:

#include<iostream>
#include<cstdio>

using namespace std;

int n,k,cf[1004][1004],ans,a[1004][1004]; 

int main() {
    scanf("%d%d",&n,&k);
    for(int i = 1;i <= n; i++) {
        int x,y,xx,yy;
        scanf("%d%d%d%d",&x,&y,&xx,&yy);
        cf[x][y]++;
        cf[xx][y]--;
        cf[x][yy]--;
        cf[xx][yy]++;
    }
    for(int i = 0;i <= 1001; i++)
        for(int j = 0;j <= 1001; j++) {
            a[i][j] = a[i-1][j] + a[i][j-1] - a[i-1][j-1] + cf[i][j];
            if(a[i][j] == k) ans++;
        }
    printf("%d",ans);
    return 0;
}