Heads up, this is a harder problem. Congratulations on making it here!

Given two arrays of ints, return a new array of ints which has all the elements from the two original arrays, alternating. That means that the output starts with the first element of a, followed by the first element of b, followed by the second element of a, then the second element of b and so forth. If you run out of elements from one array, continue on with all the remaining elements from the other array. Precondition: both inputs will have at least one element.

HINT: the output array will be sized to the length of the sum of the lengths of the input arrays.