Medium

Quiz

#526 Beautiful Arrangement

APPROACH

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 1:

Input: n = 2

Output: 2

Explanation:

The first beautiful arrangement is [1,2]:

- perm[1] = 1 is divisible by i = 1

- perm[2] = 2 is divisible by i = 2

The second beautiful arrangement is [2,1]:

- perm[1] = 2 is divisible by i = 1

- i = 2 is divisible by perm[2] = 1

Example 2:

Input: n = 1

Output: 1

1 of 4

What is the optimal approach for this problem?