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.
perm2 are different if there is some index
i such that
perm1[i] != perm2[i].
Input: nums = [1,17,8] Output: 2 Explanation: [1,8,17] and [17,8,1] are the valid permutations.
Input: nums = [2,2,2] Output: 1
1 <= nums.length <= 12
0 <= nums[i] <= 109