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 ",max(Left[1],Right[1])); 38 continue; 39 } 40 printf("%d ",dfs(1,n,1,n,sum)); 41 } 42 return 0; 43 }