最大子矩阵和 URAL 1146 Maximum Sum

 1 /*
 2     最大子矩阵和：把二维降到一维，即把列压缩；然后看是否满足最大连续子序列；
 3     好像之前做过，没印象了，看来做过的题目要经常看看:)
 4 */
 5 #include <cstdio>
 6 #include <iostream>
 7 #include <cstring>
 8 #include <algorithm>
 9 using namespace std;
10 
11 const int MAXN = 1e2 + 10;
12 const int INF = 0x3f3f3f3f;
13 int a[MAXN][MAXN];
14 int dp[MAXN][MAXN][MAXN];
15 
16 int main(void)        //URAL 1146 Maximum Sum
17 {
18     //freopen ("D.in", "r", stdin);
19 
20     int n;
21     while (scanf ("%d", &n) == 1)
22     {
23         int ans = -INF;
24         memset (dp, 0, sizeof (dp));
25         for (int i=1; i<=n; ++i)
26         {
27             for (int j=1; j<=n; ++j)
28             {
29                 scanf ("%d", &a[i][j]);
30             }
31         }
32 
33         for (int i=1; i<=n; ++i)
34         {
35             for (int j=1; j<=n; ++j)
36             {
37                 int sum = 0;
38                 for (int k=j; k>=1; --k)
39                 {
40                     sum += a[i][k];
41                     dp[i][j][k] = max (sum + dp[i-1][j][k], sum);
42                     ans = max (ans, dp[i][j][k]);
43                 }
44             }
45         }
46 
47         printf ("%d\n", ans);
48     }
49 
50     return 0;
51 }