hdu 4597 记忆化搜索

思路：定义一个四维状态的数组，记录每个状态先手的最优值。

#include<iostream>

#include<algorithm>

#include<cmath>

#include<cstring>

#include<cstdio>

#define Maxn 30

using namespace std;

int ans[Maxn][Maxn][Maxn][Maxn],suma[Maxn],sumb[Maxn];

void init()

{

    memset(ans,0,sizeof(ans));

    memset(suma,0,sizeof(suma));

    memset(sumb,0,sizeof(sumb));

}

inline int Max(int a,int b,int c,int d)

{

    a=a>b?a:b;

    c=c>d?c:d;

    return a>c?a:c;

}

int dfs(int l,int r,int l1,int r1)

{

    if(l>r&&l1>r1) return 0;

    if(ans[l][r][l1][r1]) return ans[l][r][l1][r1];

    int levsum=suma[r]-suma[l-1]+sumb[r1]-sumb[l1-1];

    int ans1=0,ans2=0,ans3=0,ans4=0;

    if(l<=r){

        ans1=levsum-dfs(l+1,r,l1,r1);

        ans2=levsum-dfs(l,r-1,l1,r1);

    }

    if(l1<=r1){

        ans3=levsum-dfs(l,r,l1+1,r1);

        ans4=levsum-dfs(l,r,l1,r1-1);

    }

    return ans[l][r][l1][r1]=Max(ans1,ans2,ans3,ans4);

}

int main()

{

    int n,i,j,t,x;

    scanf("%d",&t);

    while(t--){

        init();

        scanf("%d",&n);

        for(i=1;i<=n;i++){

            scanf("%d",&x);

            suma[i]=suma[i-1]+x;

        }

        for(i=1;i<=n;i++){

            scanf("%d",&x);

            sumb[i]=sumb[i-1]+x;

        }

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

    }

    return 0;

}