Leetcode 2122: Recover the Original Array

In this problem, one array was “mixed up” and we are trying to recover the original array. Any valid possibility is okay to return and we don’t need to return the entire set of valid answers.

Alice had a 0-indexed array arr consisting of n positive integers. She chose an arbitrary positive integer k and created two new 0-indexed integer arrays lower and higher in the following manner:
lower[i] = arr[i] - k, for every index i where 0 <= i < n
higher[i] = arr[i] + k, for every index i where 0 <= i < n

Unfortunately, Alice lost all…