HDU 4597 Play Game (memory-based search)

There are two piles of n cards and each card has a score. Alice and Bob take the cards at both ends of the two cards in turn.

Ask Alice to get the highest score;

#include 
 
    #include 
  
     #include   #include 
   
      #include 
    
      #include 
     
        #define M 50  #define LL long long  using namespace std;int n;int dp[M][M][M][M];int x[M],y[M],sum1[M],sum2[M];int dfs(int a,int b,int c,int d){if(dp[a][b][c][d]) return dp[a][b][c][d];if(a>b&&c>d) return 0;int ans1=0,ans2=0;if(a<=b){ans1=max(x[a]+dfs(a+1,b,c,d),x[b]+dfs(a,b-1,c,d));}if(c<=d){ans2=max(y[c]+dfs(a,b,c+1,d),y[d]+dfs(a,b,c,d-1));}return dp[a][b][c][d]=sum1[b]-sum1[a-1]+sum2[d]-sum2[c-1]-max(ans1,ans2);  }int main(){int t;scanf("%d",&t);while(t--){   scanf("%d",&n);memset(dp,0,sizeof(dp));sum1[0]=0;sum2[0]=0;for(int i=1;i<=n;i++){scanf("%d",&x[i]);sum1[i]=sum1[i-1]+x[i];}for(int i=1;i<=n;i++){   scanf("%d",&y[i]);sum2[i]=sum2[i-1]+y[i];}printf("%d\n",sum1[n]+sum2[n]-dfs(1,n,1,n));}return 0;}