Arrange the Bulls

题目链接

复制代码

#include <stdio.h>
#include <algorithm>
#include <string.h>
#include <iostream>
using namespace std;
typedef long long ll;

inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

/********************************************************************/

const int maxn = 25;
int n, m;
int dp[(1<<20)+5];
int ok[maxn][maxn];

void solve(){
    dp[0] = 1;
    for(int i = 1;i <= n;i++){
        for(int j = (1<<m);j >= 0;j--){
            if(dp[j]){ //j状态有i-1头牛
                for(int k = 1;k <= m;k++){  //每一个牛棚
                    if(ok[i][k] && (j != (j|(1<<(k-1)))))
                        dp[j|(1<<(k-1))] += dp[j];
                }
            }
            dp[j] = 0;
        }
    }
    int ans = 0;
    for(int i = 0;i < (1<<m);i++){
        ans += dp[i];
    }
    printf("%d\n", ans);
    return;
}

int main(){
    while(~scanf("%d%d", &n ,&m)){
        memset(ok, 0, sizeof(ok));
        memset(dp, 0, sizeof(dp));

        for(int i = 1;i <= n;i++){
            int a, b;
            a = read();
            while(a--){
                b = read();
                ok[i][b] = 1;
            }
        }
        solve();
    }
    return 0;
}