0996. Number of Squareful Arrays

https://leetcode.com/problems/number-of-squareful-arrays

Description

An array is squareful if the sum of every pair of adjacent elements is a perfect square.

Given an integer array nums, return the number of permutations of nums that are squareful.

Two permutations perm1 and perm2 are different if there is some index i such that perm1[i] != perm2[i].

Example 1:

**Input:** nums = [1,17,8]
**Output:** 2
**Explanation:** [1,8,17] and [17,8,1] are the valid permutations.

Example 2:

**Input:** nums = [2,2,2]
**Output:** 1

Constraints:

• 1 <= nums.length <= 12

• 0 <= nums[i] <= 109

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