Copy all elements of a array to another array at the specified index

I want to copy all elements of an array to another at a specified location.

Eg:

Array A contains {'a', 'b', 'c', 'd'}

Array B contains {'x','y', 'z'}

Array C should now contain {'a', 'x', 'y', 'z', 'b', 'c', 'd'} when `insert-index`  is 1 (insert all B's at first index of A)

My preferred programming is in Java or in C#

pseudo-code of my try:

//Copy all the elements of the first array to the output array till the index //Copies 'a' to the output array

for(int i=0;i<insert-index;i++)
output[i] = A[i]

//Copy all the elements of the destination array to the output array //copies 'x','y','z' to the output array

for(int i=0;i<B.Array.Length;i++)
output[i] = B[i]

//copy all the elements of the source array to the output array. //copies remaining 'b', 'c', 'd'

for(int i=0;i<A.Array.Length-index;i++)
output[i]=A[i]

The best shot at the algorithm I could give is O(n power 3)

Can any body tell me how else to approach or any pointers is greatly appreciated.

(EDIT: I know i could use Array.Copy or memcpy kind of internal functionality. But, I am just trying to learn how did they do it and also to improvise my prgm stuff.)

Solution

You just need to think through what the starting and ending indices need to be.
I've included some comments below.

// this part is straightforward
for (int i = 0; i < insert-index; i++)
  output[i] = A[i]

// we already have insert-index items in output, so continue from there
for (int i = 0; i < B.length; i++)
  output[insert-index + i] = B[i]

// we already have (B.length + insert-index) items in output,
//   and we've already used insert-index items from A, so continue from there
for (int i = insert-index; i < A.length; i++)
  output[B.length + i] = A[i]

Since we're only touching each element of A and B once, it's O(n). But it would probably be better to say it's O(m + n), where m and n are the lengths of A and B respectively.