# Leetcode 526 - Beautiful Arrangement

Note:

• Use backtracking to find all permutations.
• While doing dfs, pre-check if it meets the requirement of beautiful arrangements.

Question:

Suppose you have n integers labeled 1 through n. A permutation of those n integers perm (1-indexed) is considered a beautiful arrangement if for every i (1 <= i <= n), either of the following is true:

• perm[i] is divisible by i.
• i is divisible by perm[i].

Given an integer n, return the number of the beautiful arrangements that you can construct.

Example:

Code: