ArrayNesting.cpp

/*
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:
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
*/

class Solution {
public:
    int arrayNesting(vector<int>& nums) {
        int n=nums.size(), result=0;
        vector<bool> vis(n,false);
        for(auto num : nums){
            if(vis[num]) continue;
            int len=0;
            while(!vis[num]){
                vis[num]=true;
                num=nums[num];
                len++;
            }
            result=max(result,len);
        }
    return result;
    }
};