Merge Sort - C++

gistfile1.cpp

int* mergesort(int input[], size_t length)
{
	if(length == 1)
	{
		return input;
	}
	int pivot = length/2;
	size_t a_length = pivot;
	size_t b_length = length-pivot;
	int *a = mergesort(input, a_length);
	int *b = mergesort(input + pivot, b_length);
	return merge(a, b, a_length, b_length);
}

int* merge(int left[], int right[], size_t left_length, size_t right_length)
{
	int i = 0, j = 0, k = 0;
	int* merged = new int[left_length + right_length];
	while(i < left_length && j < right_length)
	{
		if(left[i] < right[j]) {
			merged[k++] = left[i++];
		} else {
			merged[k++] = right[j++];
		}
	}
	while(i < left_length) {
		merged[k++] = left[i++];
	}
	while(j < right_length) {
		merged[k++] = right[j++];
	}
	return merged;
}