洛谷 P2004 领地选择

题目传送门

解题思路:

二维前缀和.
AC代码:

 1 #include<iostream>
 2 #include<cstdio>
 3 
 4 using namespace std;
 5 
 6 int n,m,c,g[1001][1001],ansi = 1,ansj = 1;
 7 long long a[1001][1001],k[1001][1001],ans = -1999999999;
 8 //ans一定要初始化,-9999999都不行 
 9 
10 int main() {
11     scanf("%d%d%d",&n,&m,&c);
12     for(int i = 1;i <= n; i++)
13         for(int j = 1;j <= m; j++)
14             scanf("%d",&g[i][j]);
15     for(int i = 1;i <= n; i++)
16         for(int j = 1;j <= m; j++) {
17             a[i][j] = a[i-1][j] + a[i][j-1] - a[i-1][j-1] + g[i][j];
18             if(i >= c && j >= c) {
19                 k[i][j] = a[i][j] - a[i-c][j] - a[i][j-c] + a[i-c][j-c];
20                 if(k[i][j] > ans) {
21                     ans = k[i][j];
22                     ansi = i - c + 1;
23                     ansj = j - c + 1;
24                 }
25             }
26         }
27     printf("%d %d",ansi,ansj);
28     return 0;
29 }