{leetcode}/problems/number-of-squareful-arrays/[LeetCode - Number of Squareful Arrays^]
Given an array A of non-negative integers, the array is squareful if for every pair of adjacent elements, their sum is a perfect square.
Return the number of permutations of A that are squareful. Two permutations A1 and A2 differ if and only if there is some index i such that A1[i] != A2[i].
Example 1:
Input: [1,17,8] Output: 2 Explanation: [1,8,17] and [17,8,1] are the valid permutations.
Example 2:
Input: [2,2,2] Output: 1
Note:
-
1 ⇐ A.length ⇐ 12 -
0 ⇐ A[i] ⇐ 1e9
link:{sourcedir}/_0996_NumberOfSquarefulArrays.java[role=include]