merge sorted array

 1def merge_two_sorted_arrays(A, m, B, n):
 2
 3    a, b, write_idx = m - 1, n - 1, m + n - 1
 4    while a >= 0 and b >= 0:
 5        if A[a] > B[b]:
 6            A[write_idx] = A[a]
 7            a -= 1
 8        else:
 9            A[write_idx] = B[b]
10            b -= 1
11        write_idx -= 1
12    while b >= 0:
13        A[write_idx] = B[b]
14        write_idx, b = write_idx - 1, b - 1

1A = [1,2,3,4,0,0,0]
2B = [4,5,6]
3a = 4
4b = 3

1A = [1,2,3,4,4,5,6]
2B = [4,5,6]
3a = 4
4b = 3