BZOJ1742[Usaco2005 nov]Grazing on the Run 边跑边吃草

费用提前计算的DP..

 1 #include <iostream>
 2 #include <algorithm>
 3 #include <cstdio>
 4 #include <cstring>
 5 using namespace std;
 6 #define INF 0x3f3f3f3f
 7 #define MAXN 1005
 8 int dp[2][MAXN][MAXN];
 9 int x[MAXN];
10 int n,x0;
11 int main()
12 {
13     scanf("%d%d",&n,&x0);
14     for(int i=1;i<=n;i++)
15         scanf("%d",&x[i]);
16     x[++n]=x0;
17     sort(x+1,x+n+1);
18     for(int i=1;i<=n;i++)
19         if(x[i]!=x0)dp[0][i][i]=dp[1][i][i]=INF;
20         else
21             dp[0][i][i]=dp[1][i][i]=0;
22     for(int i=n;i>=1;i--)
23         for(int j=i+1;j<=n;j++)
24         {
25             dp[0][i][j]=min(dp[0][i+1][j]+(x[i+1]-x[i])*(n-j+i),
26                             dp[1][i+1][j]+(x[j]-x[i])*(n-j+i));
27             dp[1][i][j]=min(dp[1][i][j-1]+(x[j]-x[j-1])*(n-j+i),
28                             dp[0][i][j-1]+(x[j]-x[i])*(n-j+i));
29         }
30         printf("%d\n",min(dp[0][1][n],dp[1][1][n]));
31         return 0;
32 }