Maximum Employees to Be Invited to a Meeting

class Solution(object):
    def maximumInvitations(self, favorite):
        """
        :type favorite: List[int]
        :rtype: int
        """
        def findCycleLen(ele):
            if vis[ele]:
                return 1, ele#cycle len, cycle start

            vis[ele] = 1
            clen, clast = findCycleLen(favorite[ele])

            if ele == clast:
                self.res = max(self.res, clen)

            return clen+1, clast

        self.res = 0
        n = len(favorite)
        vis = [0]*n

        roots = set()
        for i in range(n):
            if favorite[favorite[i]] == i:
                roots.add(i)

        adj = [set() for _ in range(n)]
        for i in range(n):
            if i not in roots:
                adj[favorite[i]].add(i)

        for i in roots:
            d = 1
            st = deque((e, 2) for e in adj[i])
            while st:
                curr = st.pop()
                for e in adj[curr[0]]:
                    st.append((e, curr[1]+1))
                d = max(d, curr[1])
            self.res += d

        for i in range(n):
            if not vis[i]:
                findCycleLen(i)

        return self.res