# LeetCode Array Nesting

LeetCode Array Nesting

A zero-indexed array A consisting of N different integers is given. The array contains all integers in the range [0, N - 1].

Sets S[K] for 0 <= K < N are defined as follows:

S[K] = { A[K], A[A[K]], A[A[A[K]]], ... }.

Sets S[K] are finite for each K and should NOT contain duplicates.

Write a function that given an array A consisting of N integers, return the size of the largest set S[K] for this array.

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 array A is an integer within the range [0, N-1].

class Solution {
private:
int nest(vector<int> &nums, vector<int> &visited, int k) {
int ans = 0;
while (visited[k] == 0) {
visited[k] = 1;
++ans;
k = nums[k];
}
return ans;
}
public:
int arrayNesting(vector<int>& nums) {
int n = nums.size();
vector<int> visited(n, 0);
int ans = 0;
for (int i = 0; i < nums.size(); ++i) {
if (visited[i] == 0) {
int cur = nest(nums, visited, i);
ans = max(ans, cur);
}
}
return ans;
}
};