This function swaps the even-index values of the array with their odd-index pairs, but only when the earlier value is greater than the later value. Thus, the element at index 0 is (potentially) swapped with the element at index 1, the element with index 2 is (potentially) swapped with the element at index 3, and so on. Note that this function returns a whole array, not just an int. Precondition: the input array's length will be an even number.