poj 2738 Two Ends

 题目：http://poj.org/problem?id=2738

 没什么好说的，记忆化搜索···

 

 #include<stdio.h>
 #include<string.h>
 #include<algorithm>
 using namespace std;
 int a[1005];
 int dp[1005][1005];
 int max(int i,int j)
 {
	 return i>j?i:j;
 }
 int dfs(int left,int right)
 {
     if(dp[left][right]!=-1)
         return dp[left][right];
     else if(left==right-1)
     {
         return dp[left][right]=abs(a[left]-a[right]);
     }
     else
     {
         int tp1,tp2;
         if(a[left+1]>=a[right])
             tp1=dfs(left+2,right)+a[left]-a[left+1];
         else
             tp1=dfs(left+1,right-1)+a[left]-a[right];
         if(a[left]>=a[right-1])
             tp2=dfs(left+1,right-1)+a[right]-a[left];
         else
             tp2=dfs(left,right-2)+a[right]-a[right-1];
         return dp[left][right]=max(tp1,tp2);
     }
 }
 int main()
 {
     int n,cas=0;
     while(scanf("%d",&n)&&n)
     {
         memset(dp,-1,sizeof(dp));
         for(int i=0;i<n;i++)
             scanf("%d",a+i);
         printf("In game %d, the greedy strategy might lose by as many as %d points.\n",cas++,dfs(0,n-1));
     }
     return 0;
 }