Given two sorted integer arrays arr1 and arr2 where length of arr1 is equal or larger than length of arr2. The array arr1 has exactly x vacant cells, which is equal to the difference in length between two arrays. Merge the elements of arr2 in their correct position in array arr1 and return the final array.
Let array arr1 equal to [ 0, 2, 0, 3, 0, 5, 6, 0, 0 ] and array arr2 equal to [ 1, 8, 9, 10, 15 ].
The vacant cells in arr1 are represented by 0. After we merge arr2 into arr1 the expected array is [ 1, 2, 3, 5, 6, 8, 9, 10, 15 ]. The solution is expected to return this array.