[daily question] 565. Array nesting

565. Array nesting
Input : A = [5,4,0,3,1,6,2]
Output : 4
explain :
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}

The output is length ..

Regular simulation questions

take A[i] And A[A[i]] There is a directed edge between , Because all numbers range in [0,N−1], And not repeated , So there is at least one ring , The essence of the problem is Find the maximum length of all rings .

Directly simulate according to the meaning of the title , Deal with each... From front to back nums[i], And try to from nums[i] Start and traverse the ring in which it is located , In order to prevent some rings from being processed repeatedly , For the currently passed nums[i] Marked as −1, In this way, each number can be accessed no more than 3 Time , The overall complexity is O(n).

class Solution { 
    
    public