HDU 4957 Play Game(记忆化）

Play Game

#include <cstdio>
#include <cstdlib>
#include <iostream>
#include <cstring>

using namespace std;

const int maxn = 20 + 5;

int a[maxn];
int b[maxn];
int suma[maxn], sumb[maxn];
//dp[la][ra][lb][rb]表示当前玩家从a堆的la~ra,b堆的lb~rb能获得的最大价值
int dp[maxn][maxn][maxn][maxn];

int dfs(int al,int ar,int bl,int br) {
    if(dp[al][ar][bl][br] != -1)
        return dp[al][ar][bl][br];

    dp[al][ar][bl][br] = 0;
    //取走当前数+对手留给我的分
    if(al <= ar)
        dp[al][ar][bl][br] = a[al] + (suma[ar]-suma[al]+sumb[br]-sumb[bl-1]-dfs(al+1,ar,bl,br));

    if(al <= ar)
        dp[al][ar][bl][br] = max(dp[al][ar][bl][br], a[ar] + (suma[ar-1]-suma[al-1]+sumb[br]-sumb[bl-1]-dfs(al,ar-1,bl,br)));

    if(bl <= br)
        dp[al][ar][bl][br] = max(dp[al][ar][bl][br], b[bl] + (suma[ar]-suma[al-1]+sumb[br]-sumb[bl]-dfs(al,ar,bl+1,br)));

    if(bl <= br)
        dp[al][ar][bl][br] = max(dp[al][ar][bl][br], b[br] + (suma[ar]-suma[al-1]+sumb[br-1]-sumb[bl-1]-dfs(al,ar,bl,br-1)));

    return  dp[al][ar][bl][br];
}

int main() {
   // freopen("data.in", "r", stdin);
    int t;
    scanf("%d",&t);
    while(t--) {
        int n;
        scanf("%d",&n);
        suma[0] = 0;
        sumb[0] = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d",&a[i]);
            suma[i] = suma[i-1] + a[i];
        }
        for(int i = 1; i <= n; i++) {
            scanf("%d",&b[i]);
            sumb[i] = sumb[i-1]+b[i];
        }
        memset(dp,-1,sizeof(dp));
        printf("%d\n",dfs(1,n,1,n));
    }
    return 0;
}