POJ - 1847Tram最短路

3 2 1
2 2 3
2 3 1
2 1 2

0

/*
 *Author: 2486
 *Memory: 716 KB    Time: 16 MS
 *Language: G++     Result: Accepted
 */
//理解题目意思，看懂题目即可
//其中注意细节,开关最开始的方向是由第一个数的值所确定的，所以对于第一个数的
//状态是不需要进行开关操作的
#include <iostream>
#include <cstring>
#include <string>
#include <cstdio>
#include <algorithm>
using namespace std;
const int INF = 0x3f3f3f3f;
const int N = 100 + 5;
int n,a,b,x,y;
int d[N][N];

int warshall_floyd() {
    for(int  i = 0 ; i <= n; i ++) {
        d[i][i] = 0;
    }
    for(int k = 1; k <= n; k ++) {
        for(int i = 1 ; i <= n; i ++) {
            for(int j = 1; j <= n ; j ++) {
                d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
            }
        }
    }
}


int main() {
    while(~scanf("%d%d%d",&n,&a,&b)) {
        memset(d,0x3f,sizeof(d));
        for(int i = 1; i <= n; i ++) {
            scanf("%d",&x);
            for(int j = 0; j < x; j ++) {
                scanf("%d",&y);
                if(j) d[i][y] = 1;
                else  d[i][y] = 0;
            }
        }
        warshall_floyd();
        if(d[a][b] != INF)printf("%d\n",d[a][b]);
        else printf("-1\n");
    }
    return 0;
}