leetcode

0 class Solution {

1 public:

2 vector<int> findOrder(int n, vector<vector<int>> &prerequisites) {

3 vector<vector<int>> adj(n);

4 vector<int> count(n, 0);

5 vector<int> res;

6 int num = 0;

7

8 for (auto &p : prerequisites) {

9 adj[p[1]].push_back(p[0]);

10 count[p[0]]++;

11 }

12

13 queue<int> q;

14 for (int i = 0; i < n; i++)

15 if (!count[i]) q.push(i);

16

17 while (!q.empty()) {

18 int root = q.front();

19 q.pop();

20 res.push_back(root);

21 n--;

22 for (int c : adj[root])

23 if (!--count[c]) q.push(c);

24 }

25 return n == 0 ? res : vector<int>();

26 }

27 };