竟食后人（TLE[20,30]）

bool bfs(int sc) {
	memset(dep, 0, sizeof (int) * (sc + 1));
	queue<int> q;
	q.push(s), dep[s] = 1;
	while (q.size()) {
		int u = q.front(); q.pop();
		for (int i = head[u]; ~i; i = g[i].nxt) 
			if (g[i].w && !dep[g[i].v]) q.push(g[i].v), dep[g[i].v] = dep[u] + 1;
	}
	return dep[t];
}

bool bfs(int sc) {
	memset(dep, 0, sizeof (int) * (sc + 1));
	queue<int> q;
	q.push(s);//dep[s]赋值错误，导致可以倒回来更新dep[s]
	while (q.size()) {
		int u = q.front(); q.pop();
		for (int i = head[u]; ~i; i = g[i].nxt) 
			if (g[i].w && !dep[g[i].v]) q.push(g[i].v), dep[g[i].v] = dep[u] + 1;
	}
	return dep[t];
}