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.
Each element of A is an integer within the range [0, N-1].
Solution:
class Solution {
public int arrayNesting(int[] nums) {
int n = nums.length;
int max = 0;
boolean[] visited = new boolean[n];
for (int i = 0; i < n; i ++) {
if (!visited[i]) {
max = Math.max(max, dfs(nums, i, visited));
}
}
return max;
}
private int dfs(int[] nums, int i, boolean[] visited) {
if (visited[i]) return 0;
visited[i] = true;
return 1 + dfs(nums, nums[i], visited);
}
}