public class Solution
extends Object
996 - Number of Squareful Arrays\.
Hard
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