human
I found an interesting problem on https://leetcode.com/problems/array-nesting/:
A zero-indexed array A of length N contains all integers from 0 to N-1. Find and return the longest length of set S, where S[i] = {A[i], A[A[i]], A[A[A[i]]], ... } subjected to the rule below.

Suppose the first element in S starts with the selection of element A[i] of index = i, the next element in S should be A[A[i]], and then A[A[A[i]]]… By that analogy, we stop adding right before a duplicate element occurs in S.

Example 1:

Input: A = [5,4,0,3,1,6,2]
Output: 4
Explanation: 
A[0] = 5, A[1] = 4, A[2] = 0, A[3] = 3, A[4] = 1, A[5] = 6, A[6] = 2.

One of the longest S[K]:
S[0] = {A[0], A[5], A[6], A[2]} = {5, 6, 2, 0}

Note:

N is an integer within the range [1, 20,000].
The elements of A are all distinct.
Each element of A is an integer within the range [0, N-1].

I tried it in Python, but could not do it. Can you solve it?
assistant
#Here is Python code to find and return the longest length of set S, where S[i] = {A[i], A[A[i]], A[A[A[i]]], .

class Solution:
     def arrayNesting(self, nums):
         """
         :type nums: List[int]
         :rtype: int
         """
 
         
         dic = set()
         ma = 0
         for i in nums:
             if i not in dic: # not considered
                 set_ = set()
                 while i  not in set_:
                     set_.add(i)
                     i = nums[i]
                 ma = max(ma,len(set_))
                 dic.update(set_)
         return ma