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Array Nesting - Array - Medium - LeetCode - MiniTV

Array Nesting - Array - Medium - LeetCode - मिनी टीवी

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].

public class Solution {
    Dictionary<int,int> T = new Dictionary<int,int>();
    public int ArrayNesting(int[] nums) {
        int max = int.MinValue;
        for(int i=0;i<nums.Length;i++){
            max = Math.Max(max, Helper(nums, i));
        }
        
        return max-1;
    }
    
    private int Helper(int[] nums, int index){
        int val = 0;
        T.TryGetValue(index, out val);
        if(val != 0){
            return val;
        }
        
        T[index] = 1;
        return 1 + Helper(nums, nums[index]);
    }
}

Time Complexity: O(n)

Space Complexity: O(n)