leetcode

0 class Solution {

1 public:

2 int longestCycle(vector<int> &edges) {

3 int n = edges.size(), res = -1;

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

5 for (int edge : edges)

6 if (edge != -1) count[edge]++;

7

8 queue<int> q;

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

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

11

12 while (!q.empty()) {

13 int root = q.front();

14 q.pop();

15 if (edges[root] == -1) continue;

16 if (--count[edges[root]] == 0) q.push(edges[root]);

17 }

18

19 for (int i = 0; i < n; i++) {

20 if (!count[i]) continue;

21 int k = i, num = 1;

22 while (edges[k] != i) {

23 count[k] = 0;

24 k = edges[k];

25 num++;

26 }

27 res = max(res, num);

28 }

29

30 return res;

31 }

32 };