HDU 4597 Play Game

Alice and Bob are playing a game. There are two piles of cards. There are N cards in each pile, and each card has a score. They take turns to pick up the top or bottom card from either pile, and the score of the card will be added
to his total score. Alice and Bob are both clever enough, and will pick up cards to get as many scores as possible. Do you know how many scores can Alice get if he picks up first?

Input

The first line contains an integer T (T≤100), indicating the number of cases.

Each case contains 3 lines. The first line is the N (N≤20). The second line contains N integer ai (1≤a
i≤10000). The third line contains N integer b i (1≤bi≤10000).

Output

For each case, output an integer, indicating the most score Alice can get.

Sample Input

2

1
23
53

3
10 100 20
2 4 3

Sample Output

53
105
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;

#define MAXN 22
int dp[MAXN][MAXN][MAXN][MAXN],aa[MAXN],bb[MAXN];

int dfs(int a,int b,int c,int d,int sum)
{
if(dp[a][b][c][d]) return dp[a][b][c][d];
int temp=0;

if(a<=b)
{
temp=max(temp,sum-dfs(a+1,b,c,d,sum-aa[a]));
temp=max(temp,sum-dfs(a,b-1,c,d,sum-aa[b]));
}
if(c<=d)
{
temp=max(temp,sum-dfs(a,b,c+1,d,sum-bb[c]));
temp=max(temp,sum-dfs(a,b,c,d-1,sum-bb[d]));
}
dp[a][b][c][d]=temp;
return dp[a][b][c][d];
}

int main()
{
int t,n,i,sum;
scanf("%d",&t);
while(t--)
{
sum=0;
scanf("%d",&n);
for(i=1;i<=n;i++)
{
scanf("%d",&aa[i]);
sum+=aa[i];
}
for(i=1;i<=n;i++)
{
scanf("%d",&bb[i]);
sum+=bb[i];
}
memset(dp,0,sizeof dp);
printf("%d\n",dfs(1,n,1,n,sum));
}
return 0;
}