Leetcode•Apr 05, 2026

Array Nesting

Hazrat Ali

Leetcode

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: 
nums[0] = 5, nums[1] = 4, nums[2] = 0, nums[3] = 3, nums[4] = 1, nums[5] = 6, nums[6] = 2.
One of the longest sets s[k]:
s[0] = {nums[0], nums[5], nums[6], nums[2]} = {5, 6, 2, 0}

Example 2:

Input: nums = [0,1,2]
Output: 1

Solution
var arrayNesting = function(nums) {
    const n = nums.length;
    const visited = new Array(n).fill(false);
    let maxLen = 0;

    for (let i = 0; i < n; i++) {
        if (!visited[i]) {
            let count = 0;
            let current = i;

            while (!visited[current]) {
                visited[current] = true;
                current = nums[current];
                count++;
            }

            maxLen = Math.max(maxLen, count);
        }
    }

    return maxLen;
};



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