HDU 4597 Play Game 2013 ACM-ICPC吉林通化全国邀请赛H题

九野的博客，转载请注明出处：  http://blog.csdn.net/acmmmm/article/details/10833941

题意：给定T个测试数据，下面有2副牌，每副n张，每张都有一个分值

问：2个人轮流取牌，每次取一张（从任意一副的牌顶或牌底取），先手可获得的最大分值

开始往博弈想了，这题是记忆化搜索

#include<stdio.h>
#include<algorithm>
#include<iostream>
#include<set>
#include<math.h>
#include<string.h>
#define N 25
using namespace std;
 
int card1[N],card2[N],sum1[N],sum2[N];
int dp[N][N][N][N];  // dp[below1][top1][below2][top2] 表示当2个牌堆是这样时可以取得的最大值
inline int Max(int a,int b){return a>b?a:b;}
 
int dfs(int below1,int top1,int below2,int top2){//返回 牌堆是这样时能取得的最大值
	if(dp[below1][top1][below2][top2]!=-1)return dp[below1][top1][below2][top2];
 
	if(below1>top1 && below2>top2) {//牌堆取完
		dp[below1][top1][below2][top2]=0;
		return 0;
	}
 
	int sum=0,ans=0;//sum表示剩下牌堆的总分
	if(below1<=top1)sum+= sum1[top1]-sum1[below1-1];
	if(below2<=top2)sum+= sum2[top2]-sum2[below2-1];
	if(below1<=top1){
		ans=Max(ans,sum-dfs(below1+1,top1,below2,top2));
		ans=Max(ans,sum-dfs(below1,top1-1,below2,top2));
	}
	if(below2<=top2){
		ans=Max(ans,sum-dfs(below1,top1,below2+1,top2));
		ans=Max(ans,sum-dfs(below1,top1,below2,top2-1));
	}
	return dp[below1][top1][below2][top2]=ans;
}
int main(){
	int T,i,n;scanf("%d",&T);
	while(T--)
	{
		scanf("%d",&n);
		for(i=1;i<=n;i++)scanf("%d",&card1[i]);
		for(i=1;i<=n;i++)scanf("%d",&card2[i]);
		sum1[0]=sum2[0]=0;
		for(i=1;i<=n;i++)
			sum1[i]=sum1[i-1]+card1[i],sum2[i]=sum2[i-1]+card2[i];
		memset(dp,-1,sizeof(dp));
		printf("%d\n",dfs(1,n,1,n));
	}
	return 0;
}