题目：https://pintia.cn/problem-sets/994805342720868352/problems/994805392092020736

这题基本是自己写的，BFS还是相对熟悉，但还是有遗忘的情况，事实证明不复习绝对凉凉，注意点是邻接表可以设置成Node型的

代码

  1. #include<iostream>
  2. #include<vector>
  3. #include<queue>
  4. #include<algorithm>
  5. #include<cstdio>
  6. using namespace std;
  7. const int maxn = 1010;
  8. vector<int> G[maxn];
  9. bool inq[maxn] = {false};
  10. struct Node{
  11.     int data, depth;
  12. };
  13. int n, m, l, k;
  15. int BFS(int data){
  16.     Node node;
  17.     node.data = data;
  18.     node.depth = 0;
  19.     queue<Node> q;
  20.     q.push(node);
  21.     inq[node.data] = true;
  22.     int num = 0;
  23.     while(!q.empty()){
  24.         Node top = q.front();
  25.         q.pop();
  26.         for(int i = 0; i < G[top.data].size(); i++){
  27.             Node next;
  28.             next.data = G[top.data][i];
  29.             next.depth = top.depth + 1;
  30.             if(next.depth <= l && inq[G[top.data][i]] == false){
  31.                 inq[G[top.data][i]] = true;
  32.                 q.push(next);
  33.                 num++;
  34.             }
  35.         }
  36.     }
  37.     return num;
  38. }
  40. int main(){
  41.     int follower, user_id;
  42.     scanf("%d%d", &n, &l);
  43.     for(int i = 1; i <= n; i++){
  44.         scanf("%d", &m);
  45.         for(int j = 0; j < m; j++){
  46.             scanf("%d", &follower);
  47.             G[follower].push_back(i);
  48.         }
  49.     }
  51.     scanf("%d", &k);
  52.     for(int i = 0; i < k; i++){
  53.         fill(inq, inq + maxn, false);
  54.         scanf("%d", &user_id);
  55.         int result = BFS(user_id);
  56.         printf("%d\n", result);
  57.     }
  58. }