[PAT] A1076 Forwards on Weibo

（重要！）
BFS遍历图
详见算法笔记第363页

AC代码

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<iostream>
#include<vector>
#include<queue>
using namespace std;
#define MAX 1002
struct node {
	int v;
	int level;
};
vector<node>Adj[MAX];
bool inq[MAX] = { false };
int n, maxLevel;
int numQuery;
int BFS(int s) {
	int numZF = 0;
	queue<node>q;
	node start;
	start.v = s;
	start.level = 0;
	q.push(start);
	inq[s] = true;
	while (q.size()) {
		numZF++;
		node unode = q.front();
		int u = unode.v;
		q.pop();
		for (int i = 0;i < Adj[u].size();i++) {
			node vnode = Adj[u][i];
			int v = vnode.v;
			if (inq[v] == false && unode.level < maxLevel) {
				inq[v] = true;
				vnode.level = unode.level + 1;
				q.push(vnode);
			}
		}
	}
	return numZF;
}
int main() {
	scanf("%d%d", &n, &maxLevel);
	for (int i = 1;i <= n;i++) {
		int tf;
		scanf("%d", &tf);
		node tempi;
		tempi.v = i;
		tempi.level = 0;
		for (int j = 0;j < tf;j++) {
			int idfollow;
			scanf("%d", &idfollow);
			Adj[idfollow].push_back(tempi);
		}
	}
	scanf("%d", &numQuery);
	for (int i = 0;i < numQuery;i++) {
		fill(inq, inq + MAX, false);
		int query;
		scanf("%d", &query);
		int fensi = BFS(query); 
		printf("%d\n", fensi - 1);
	}
	return 0;
}