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].
class Solution:
     def arrayNesting(self, nums):
         """
         :type nums: List[int]
         :rtype: int
         """
         maxLength = 0
         for i in range(len(nums)):
             length = 0
             j = i
             while nums[j] >= 0:
                 length += 1
                 tmp = nums[j]
                 nums[j] = -1
                 j = tmp
             maxLength = max(maxLength, length)
         return maxLength
class Solution:
     def arrayNesting(self, nums):
         """
         :type nums: List[int]
         :rtype: int
         """
         maxLength = 0
         for i in range(len(nums)):
             length = 0
             j = i
             while nums[j] >= 0:
                 length += 1
                 tmp = nums[j]
                 nums[j] = -1
                 j = tmp
             maxLength = max(maxLength, length)
         return maxLength