hdu 4597(记忆化搜索)

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4597

思路：要保证当前状态下，得到的是最优的，dfs+dp.

 1 #include<iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 using namespace std;

 6 

 7 int Left[44],Right[44];

 8 int dp[22][22][22][22];

 9 int n,ans,MAX;

10 

11 int dfs(int upl,int downl,int upr,int downr,int sum)

12 {

13     if(dp[upl][downl][upr][downr])return dp[upl][downl][upr][downr];

14     int ans=0;

15     if(upl<=downl){

16         ans=max(ans,sum-dfs(upl+1,downl,upr,downr,sum-Left[upl]));

17         ans=max(ans,sum-dfs(upl,downl-1,upr,downr,sum-Left[downl]));

18     }

19     if(upr<=downr){

20         ans=max(ans,sum-dfs(upl,downl,upr+1,downr,sum-Right[upr]));

21         ans=max(ans,sum-dfs(upl,downl,upr,downr-1,sum-Right[downr]));

22     }

23     return dp[upl][downl][upr][downr]=ans;

24 }

25 

26 int main()

27 {

28   //  freopen("1.txt","r",stdin);

29     int _case,sum;

30     scanf("%d",&_case);

31     while(_case--){

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

33         for(int i=1;i<=n;i++)scanf("%d",&Left[i]),sum+=Left[i];

34         for(int i=1;i<=n;i++)scanf("%d",&Right[i]),sum+=Right[i];

35         memset(dp,0,sizeof(dp));

36         if(n==1){

37             printf("%d\n",max(Left[1],Right[1]));

38             continue;

39         }

40         printf("%d\n",dfs(1,n,1,n,sum));

41     }

42     return 0;

43 }

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