Skip to content
Branch: master
Find file History
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.
996. Number of Squareful Arrays.go
996. Number of Squareful Arrays_test.go

996. 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
[1,8,17] and [17,8,1] are the valid permutations.

Example 2:

Input: [2,2,2]
Output: 1


  1. 1 <= A.length <= 12
  2. 0 <= A[i] <= 1e9


给定一个非负整数数组 A,如果该数组每对相邻元素之和是一个完全平方数,则称这一数组为正方形数组。

返回 A 的正方形排列的数目。两个排列 A1 和 A2 不同的充要条件是存在某个索引 i,使得 A1[i] != A2[i]。


  • 这一题是第 47 题的加强版。第 47 题要求求出一个数组的所有不重复的排列。这一题要求求出一个数组的所有不重复,且相邻两个数字之和都为完全平方数的排列。
  • 思路和第 47 题完全一致,只不过增加判断相邻两个数字之和为完全平方数的判断,注意在 DFS 的过程中,需要剪枝,否则时间复杂度很高,会超时。
You can’t perform that action at this time.