565 - Array Nesting.

Medium

You are given an integer array nums of length n where nums is a permutation of the numbers in the range [0, n - 1].

You should build a set s[k] = {nums[k], nums[nums[k]], nums[nums[nums[k]]], ... } subjected to the following rule:

• The first element in s[k] starts with the selection of the element nums[k] of index = k.

• The next element in s[k] should be nums[nums[k]], and then nums[nums[nums[k]]], and so on.

• We stop adding right before a duplicate element occurs in s[k].

Return the longest length of a set s[k].

Example 1:

Input: nums = 5,4,0,3,1,6,2

Output: 4

Explanation: nums0 = 5, nums1 = 4, nums2 = 0, nums3 = 3, nums4 = 1, nums5 = 6, nums6 = 2. One of the longest sets sk: s0 = {nums0, nums5, nums6, nums2} = {5, 6, 2, 0}

Example 2:

Input: nums = 0,1,2

Output: 1

Constraints:

• <code>1 <= nums.length <= 10⁵</code>

• 0 <= nums[i] < nums.length

• All the values of nums are unique.