51nod 1051 最大子矩阵和（dp）

Posted 2020-08-13 GraceSkyer

题目链接：51nod 1051 最大子矩阵和

实质是把最大子段和扩展到二维。读题注意m,n。。。

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<vector>
 4 #include<algorithm>
 5 #define CLR(a,b) memset((a),(b),sizeof((a)))
 6 using namespace std;
 7 const int N = 501;
 8 int dp[N][N];
 9 int main(){
10     int n, m, i, j, k, s, ans, x;
11     scanf("%d%d", &m, &n);
12     CLR(dp, 0);
13     for(i = 1; i <= n; ++i){
14         for(j = 1; j <= m; ++j){
15             scanf("%d", &x);
16             dp[i][j] = x + dp[i-1][j];
17         }
18     }
19     ans = 0;
20     for(i = 1; i <= n; ++i){
21         for(j = i; j <= n; ++j){
22             s = 0;
23             for(k = 1; k <= m; ++k){
24                 x = dp[j][k] - dp[i-1][k];
25                 if(s > 0)
26                     s += x;
27                 else
28                     s = x;
29                 ans = max(ans, s);
30             }
31         }
32     }
33     printf("%d\\n", ans);
34     return 0;
35 }

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