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[10][10],sum[10][10];
double dp[11][11][11][11][21];
int in[11][11][11][11][21];
double s[11][11][11][11];
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 == 1)
    {
        in[x1][y1][x2][y2][k] = 1;
        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-1)+s[i+1][y1][x2][y2],minz);
            minz = min(dfs(i+1,y1,x2,y2,k-1)+s[x1][y1][i][y2],minz);
        }
        for(i = y1;i < y2;i ++)
        {
            minz = min(dfs(x1,y1,x2,i,k-1)+s[x1][i+1][x2][y2],minz);
            minz = min(dfs(x1,i+1,x2,y2,k-1)+s[x1][y1][x2][i],minz);
        }
        in[x1][y1][x2][y2][k] = 1;
        return dp[x1][y1][x2][y2][k] = minz;
    }
}
int main()
{
    int i,j,k,u,v,n,temp;
    scanf("%d",&n);
    temp = 0;
    for(i = 1;i <= 8;i ++)
    {
        for(j = 1;j <= 8;j ++)
        {
            scanf("%d",&p[i][j]);
            temp += p[i][j];
        }
    }
    for(i = 1;i <= 8;i ++)
    {
        for(j = 1;j <= 8;j ++)
        {
            for(k = 1;k <= 8;k ++)
            {
                for(u = 1;u <= 8;u ++)
                {
                    for(v = 1;v <= n;v ++)
                    dp[i][j][k][u][v] = INF;
                }
            }
        }
    }
    for(i = 1;i <= 8;i ++)
    {
        for(j = 1;j <= 8;j ++)
        sum[i][j] = sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1] + p[i][j];
    }
    for(i = 1;i <= 8;i ++)
    {
        for(j = 1;j <= 8;j ++)
        {
            for(k = 1;k <= 8;k ++)
            {
                for(u = 1;u <= 8;u ++)
                {
                    s[i][j][k][u] = sum[k][u]+sum[i-1][j-1]-sum[i-1][u]-sum[k][j-1];
                    s[i][j][k][u] *= s[i][j][k][u];
                }
            }
        }
    }
    printf("%.3f
",sqrt(dfs(1,1,8,8,n)*1.0/n-(temp*1.0/n)*(temp*1.0/n)));
    return 0;
}