Problem Solving Question:
Write a function shuffle(arr)that takes input an array of numbers and returns an array by ordering the numbers in following fashion:
a1 <= a2 >= a3 <= a4 >= ....
Please note that there are multiple outputs that are possible for a given array. Your function can return one possible output. Example: If input is [2, 1, 5, 3, 11, 7], one possible output could be [2, 7, 3, 11, 1, 5]