UVA10118 Free Candies

题解:

记忆化搜索

如何判断一个数是否已经出现？应用位运算即可....

代码:

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define se second
#define fs first
#define LL long long
#define CLR(x) memset(x,0,sizeof x)
#define MC(x,y) memcpy(x,y,sizeof(x))
#define SZ(x) ((int)(x).size())
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=200100;
const int mod=1e9+7;
const int INF=1e9;

int n;
int mat[4][45];
int dp[45][45][45][45];

int DP(int *top,int st,int k)
{
    int &m=dp[top[0]][top[1]][top[2]][top[3]];
    if(m>=0) return m;
    if(top[0]==n&&top[1]==n&&top[2]==n&&top[3]==n||k==5) return m=0;
    for(int i=0;i<4;i++)
    if(top[i]<n)
    {
        int bit=1<<mat[i][top[i]];
        top[i]++;
        if(bit&st) m=max(m,DP(top,st-bit,k-1)+1);
        else       m=max(m,DP(top,st+bit,k+1));
        top[i]--;
    }
    return m;
}

int main()
{
    while(~scanf("%d",&n)&&n)
    {
        memset(dp,-1,sizeof(dp));
        for(int i=0;i<n;i++) scanf("%d%d%d%d",&mat[0][i],&mat[1][i],&mat[2][i],&mat[3][i]);
        int top[5]={0};
        printf("%d\n",DP(top,0,0));
    }
    return 0;
}