Merging 2 arrays

I have 3 arrays. The first array is an empty array index 0 to 51. This array will be the result.
The second array has less than 52 entries in order.
The third array also has less that 52 elements, but the sum of the elements in the 2nd and 3rd arrays equal 52.
The easiest way for me to explain it is as follows.
Let's assume the 3rd array as 4 elements. The indices are 0,1,2,3. Therefore, the second array has 48 elements. But, the third array has a field that contains a number from 0 to 52. This is the position where this element needs to be in the first array. The entries in the second array are placed in order in the third array skipping the filled locations from the third array.
If this sounds confusing it is because I get confused just thinking about it.

Any help would be appreciated.

Thanks