http://www.cnblogs.com/kedebug/archive/2013/04/07/3006493.html

#include<stdio.h>
#include<string.h>
#define N 45
#define C 22
int max(int a,int b)
{
    return a>b?a:b;
}
int pile[4][N],f[N][N][N][N],n,top[4];
int dfs(int s,int hash[C])
{
    int i,j,ans=0;
    if(f[top[0]][top[1]][top[2]][top[3]]!=-1)
    {
        return f[top[0]][top[1]][top[2]][top[3]];
    }
    if(s==5)//籃子滿了，末狀態
        return f[top[0]][top[1]][top[2]][top[3]]=0;
    int h[C],t[4];
    for(i=0;i<4;i++)
    {
        memcpy(h,hash,sizeof(h));
        if(top[i]!=n)//到n是拿空了
        {
            if(h[pile[i][top[i]]])//拿i堆頂,可以湊對
            {
                h[pile[i][top[i]]]=0;
                top[i]++;
                ans=max(ans,dfs(s-1,h)+1);
            }
            else
            {
                h[pile[i][top[i]]]=1;
                top[i]++;
                ans=max(ans,dfs(s+1,h));
            }
            top[i]--;
        }
    }
    return f[top[0]][top[1]][top[2]][top[3]]=ans;
}
int main()
{
    int i,j,k,l,m;
    while(scanf("%d",&n)&&n)
    {
        memset(pile,0,sizeof(pile));
        for(i=0;i<n;i++)
        {
            for(j=0;j<4;j++)
                scanf("%d",&pile[j][i]);
        }
        memset(f,-1,sizeof(f));
        memset(top,0,sizeof(top));
        int hash[C]={0};
        printf("%d\n",dfs(0,hash));
    }
    return 0;
}