洛谷 P2004 领地选择

题目传送门

解题思路:

二维前缀和.

AC代码:

#include<iostream>
#include<cstdio>

using namespace std;

int n,m,c,g[1001][1001],ansi = 1,ansj = 1;
long long a[1001][1001],k[1001][1001],ans = -1999999999;
//ans一定要初始化,-9999999都不行 

int main() {
    scanf("%d%d%d",&n,&m,&c);
    for(int i = 1;i <= n; i++)
        for(int j = 1;j <= m; j++)
            scanf("%d",&g[i][j]);
    for(int i = 1;i <= n; i++)
        for(int j = 1;j <= m; j++) {
            a[i][j] = a[i-1][j] + a[i][j-1] - a[i-1][j-1] + g[i][j];
            if(i >= c && j >= c) {
                k[i][j] = a[i][j] - a[i-c][j] - a[i][j-c] + a[i-c][j-c];
                if(k[i][j] > ans) {
                    ans = k[i][j];
                    ansi = i - c + 1;
                    ansj = j - c + 1;
                }
            }
        }
    printf("%d %d",ansi,ansj);
    return 0;
}