hdu1421 搬寝室

http://acm.hdu.edu.cn/showproblem.php?pid=1421

DP

dfs记忆化搜索写的，没空间优化

#include <stdio.h>
#include <stdlib.h>

#define N 2013

int n, k, a[N], dp[N][N];

int min(int x, int y)
{
    return x<y? x: y;
}

int sq(int x)
{
    return x*x;
}

int dfs(int i, int j)
{
    if(~dp[i][j])
    {
        return dp[i][j];
    }
    if(i == j)
    {
        dp[i][j] = dfs(i-2, j-2)+sq(a[i-1]-a[i]);
        return dp[i][j];
    }
    dp[i][j] = min(dfs(i-2, j-2)+sq(a[i-1]-a[i]), dfs(i-1, j));
    return dp[i][j];
}

int cmp(const void *a, const void *b)
{
    return *((int *)a) - *((int *)b);
}

int main()
{
    int i, j;
    while(~scanf("%d%d", &n, &k))
    {
        k <<= 1;
        for(i=1; i<=n; i++)
        {
            scanf("%d", a+i);
        }
        qsort(a+1, n, sizeof(a[0]), cmp);
        dp[0][0] = 0;
        for(i=1; i<=n; i++)
        {
            dp[i][0] = 0;
            for(j=2; j<=i; j+=2)
            {
                dp[i][j] = -1;
            }
        }
        printf("%d\n", dfs(n, k));
    }
    return 0;
}