merge_into_a

# You are given 2 sorted arrays A and B
# A has enough placeholders at the end to hold B
# Write a method to merge B into A in sorted order

# i.e.
# A = [3, 6, 8]
# B = [2, 5, 10, 11]
# => [2, 3, 5, 6, 8, 10, 11]

def get_last_item_index(arr):
    """Return the index of the last item in array"""

    index = None
    for i, item in enumerate(arr):
        if not item:
            break
        index = i
    return index

def merge_into_a(a, b):
    """Merge list B into list A."""

    index_a = get_last_item_index(a)
    index_b = get_last_item_index(b)
    index_buffer = len(a) - 1

    while index_b >= 0:
        if index_buffer > 0 and a[index_a] > b[index_b]:
            a[index_buffer] = a[index_a]
            index_a -= 1
        else:
            a[index_buffer] = b[index_b]
            index_b -= 1
        index_buffer -= 1
    return a

a = [3, 6, 8, None, None, None, None]
b = [2, 5, 10, 11]

print merge_into_a(a, b)