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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

Related Topics

[Bit Manipulation] [Array] [Math] [Dynamic Programming] [Backtracking] [Bitmask]

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