POJ 2738

没什么好想的，就是一个记忆化搜索。我第一次居然想爆搜~~~

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 1 #include<cstdio>

 2 #include<cstring>

 3 #include<algorithm>

 4 using namespace std;

 5 int a[1005];

 6 int dp[1005][1005];

 7 int dfs(int left,int right)

 8 {

 9     if(dp[left][right]!=-1)

10         return dp[left][right];

11     else if(left==right-1)

12     {

13         return dp[left][right]=abs(a[left]-a[right]);

14     }

15     else

16     {

17         int tp1,tp2;

18         if(a[left+1]>=a[right])

19             tp1=dfs(left+2,right)+a[left]-a[left+1];

20         else

21             tp1=dfs(left+1,right-1)+a[left]-a[right];

22         if(a[left]>=a[right-1])

23             tp2=dfs(left+1,right-1)+a[right]-a[left];

24         else

25             tp2=dfs(left,right-2)+a[right]-a[right-1];

26         return dp[left][right]=max(tp1,tp2);

27     }

28 }

29 int main()

30 {

31     int n,ca=0;

32     while(scanf("%d",&n)&&n)

33     {

34         memset(dp,-1,sizeof(dp));

35         for(int i=0;i<n;i++)

36             scanf("%d",a+i);

37         printf("In game %d, the greedy strategy might lose by as many as %d points.\n",++ca,dfs(0,n-1));

38     }

39     return 0;

40 }