1497. Check If Array Pairs Are Divisible by k

https://leetcode.com/problems/check-if-array-pairs-are-divisible-by-k

Description

Given an array of integers arr of even length n and an integer k.

We want to divide the array into exactly n / 2 pairs such that the sum of each pair is divisible by k.

Return True If you can find a way to do that or False otherwise.

Example 1:

**Input:** arr = [1,2,3,4,5,10,6,7,8,9], k = 5
**Output:** true
**Explanation:** Pairs are (1,9),(2,8),(3,7),(4,6) and (5,10).

Example 2:

**Input:** arr = [1,2,3,4,5,6], k = 7
**Output:** true
**Explanation:** Pairs are (1,6),(2,5) and(3,4).

Example 3:

**Input:** arr = [1,2,3,4,5,6], k = 10
**Output:** false
**Explanation:** You can try all possible pairs to see that there is no way to divide arr into 3 pairs each with sum divisible by 10.

Example 4:

**Input:** arr = [-10,10], k = 2
**Output:** true

Example 5:

**Input:** arr = [-1,1,-2,2,-3,3,-4,4], k = 3
**Output:** true

Constraints:

• arr.length == n

• 1 <= n <= 105

• n is even.

• -109 <= arr[i] <= 109

• 1 <= k <= 105

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