POJ 1191 棋盘分割(DP)

题目链接

大体思路看，黑书。。。其他就是注意搞一个in数组，这样记忆化搜索，貌似比较快。

 #include <cstdio>
 #include <cstring>
 #include <iostream>
 #include <cmath>
 using namespace std;
 #define INF 0x7fffffff
 int p[][],sum[][];
 double dp[][][][][];
 int in[][][][][];
 double s[][][][];
 int dfs(int x1,int y1,int x2,int y2,int k)
 {
     int i;
     if(in[x1][y1][x2][y2][k])
     return dp[x1][y1][x2][y2][k];
     if(k == )
     {
         in[x1][y1][x2][y2][k] = ;
         return dp[x1][y1][x2][y2][k] = s[x1][y1][x2][y2];
     }
     else
     {
         double minz = INF;
         for(i = x1;i < x2;i ++)
         {
             minz = min(dfs(x1,y1,i,y2,k-)+s[i+][y1][x2][y2],minz);
             minz = min(dfs(i+,y1,x2,y2,k-)+s[x1][y1][i][y2],minz);
         }
         for(i = y1;i < y2;i ++)
         {
             minz = min(dfs(x1,y1,x2,i,k-)+s[x1][i+][x2][y2],minz);
             minz = min(dfs(x1,i+,x2,y2,k-)+s[x1][y1][x2][i],minz);
         }
         in[x1][y1][x2][y2][k] = ;
         return dp[x1][y1][x2][y2][k] = minz;
     }
 }
 int main()
 {
     int i,j,k,u,v,n,temp;
     scanf("%d",&n);
     temp = ;
     for(i = ;i <= ;i ++)
     {
         for(j = ;j <= ;j ++)
         {
             scanf("%d",&p[i][j]);
             temp += p[i][j];
         }
     }
     for(i = ;i <= ;i ++)
     {
         for(j = ;j <= ;j ++)
         {
             for(k = ;k <= ;k ++)
             {
                 for(u = ;u <= ;u ++)
                 {
                     for(v = ;v <= n;v ++)
                     dp[i][j][k][u][v] = INF;
                 }
             }
         }
     }
     for(i = ;i <= ;i ++)
     {
         for(j = ;j <= ;j ++)
         sum[i][j] = sum[i-][j] + sum[i][j-] - sum[i-][j-] + p[i][j];
     }
     for(i = ;i <= ;i ++)
     {
         for(j = ;j <= ;j ++)
         {
             for(k = ;k <= ;k ++)
             {
                 for(u = ;u <= ;u ++)
                 {
                     s[i][j][k][u] = sum[k][u]+sum[i-][j-]-sum[i-][u]-sum[k][j-];
                     s[i][j][k][u] *= s[i][j][k][u];
                 }
             }
         }
     }
     printf("%.3f\n",sqrt(dfs(,,,,n)*1.0/n-(temp*1.0/n)*(temp*1.0/n)));
     return ;
 }