Array Nesting.cpp

PROBLEM:


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:

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



SOLUTION:


class Solution {
public:
    int arrayNesting(vector<int>& nums) {
        
        int i,k,n,ans=INT_MIN,c;
        n=nums.size();
        
        vector<bool> vis(n,false);
        
        for(i=0;i<n;i++)
        {
            if(!vis[i])
            {
                vis[i]=true;
                k=nums[i];
                c=1;
                
                while(!vis[k])
                {   
                    vis[k]=true;
                    c++;
                    k=nums[k];
                }
                
                ans=max(ans,c);
            }
        }
        
        return ans;
    }
};