POJ 1847

#include<iostream>

#include<string>

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<algorithm>

#include<cmath>

#include<vector>

#define MAXN 105

#define MAXM 305

#define MOD 10000

#define inf 100000000

#define eps 1e-9

#define pi acos(-1.0)

typedef long long LL;

using namespace std;

int n, s, e, x, u, mat[MAXN][MAXN], dis[MAXN];

bool vis[MAXN];

void Dijkstra() {

memset(vis, false, sizeof(vis)); vis[s] = true;

for (int i = 1; i <= n; i++) 

dis[i] = mat[s][i];

dis[s] = 0;

for (int i = 1; i < n; i++) {

int k = -1;

for (int j = 1; j <= n; j++) {

if (!vis[j] && (k == -1 || dis[j] < dis[k])) 

k = j;

}

if (k == -1) continue;

vis[k] = true;

for (int j = 1; j <= n; j++) {

if (!vis[j] && dis[k] + mat[k][j] < dis[j])

dis[j] = dis[k] + mat[k][j];

}

}

}

int main() {

//freopen("in.txt", "r", stdin);

//freopen("out.txt", "w", stdout);

scanf("%d %d %d", &n, &s, &e);

for (int i = 1; i <= n; i++) 

for (int j = 1; j <= n; j++) 

mat[i][j] = inf;

for (int i = 1; i <= n; i++) {

scanf("%d", &x);

for (int j = 1; j <= x; j++) {

scanf("%d", &u);

(j == 1) ? mat[i][u] = 0 : mat[i][u] = 1;

}

}

Dijkstra();

if (dis[e] == inf) puts("-1");

else printf("%d\n", dis[e]);

    return 0;

}