UVa 10827 - Maximum sum on a torus

　　题目大意：UVa 108 - Maximum Sum的加强版，求最大子矩阵和，不过矩阵是可以循环的，矩阵到结尾时可以循环到开头。开始听纠结的，想着难道要分情况讨论吗？！就去网上搜，看到可以通过补全进行处理，也是，通过补全一个相同的，问题就迎刃而解了，所以把n*n的矩阵扩展成2n*2n的矩阵就好了。

 #include <cstdio>
 #include <cstring>
 #define MAXN 160

 int a[MAXN][MAXN], sum[MAXN][MAXN];

 int main()
 {
 #ifdef LOCAL
     freopen("in", "r", stdin);
 #endif
     int T;
     scanf("%d", &T);
     while (T--)
     {
         int n;
         scanf("%d", &n);
         memset(sum, , sizeof(sum));
         for (int i = ; i <= n; i++)
         {
             for (int j = ; j <= n; j++)
                 scanf("%d", &a[i][j]);
             for (int j = n+; j <= *n; j++)
                 a[i][j] = a[i][j-n];
         }
         for (int i = n+; i <= *n; i++)
             for (int j = ; j <= *n; j++)
                 a[i][j] = a[i-n][j];
         for (int i = ; i <= *n; i++)
             for (int j = ; j <= *n; j++)
                 sum[i][j] = sum[i][j-] + sum[i-][j] - sum[i-][j-] + a[i][j];
         int max = a[][];
         for (int i = ; i <= n; i++)
             for (int p = ; p < n; p++)
                 for (int j = ; j <= n; j++)
                     for (int q = ; q < n; q++)
                     {
                         int t = sum[i+p][j+q] - sum[i+p][j-] - sum[i-][j+q] + sum[i-][j-];
                         if (t > max)   max = t;
                     }
         printf("%d\n", max);
     }
     return ;
 }