13_归并排序

def merge_sort_list(sort_a, sort_b):
    length_a, length_b =len(sort_a), len(sort_b)
    a = b = 0
    new_sorted_seq = list()
    # 实际在len=1 才比较
    while a < length_a and b < length_b:
        if sort_a[a] < sort_b[b]:
            new_sorted_seq.append(sort_a[a])
            a += 1
        else:
            new_sorted_seq.append(sort_b[b])
            b += 1
    if a < length_a:
        new_sorted_seq.extend(sort_a[a:])
    else:
        new_sorted_seq.extend(sort_b[b:])
    return new_sorted_seq

def merge_sort(seq):
    if len(seq) <= 1:
        return seq
    else:
        mid = int(len(seq)/2)
        left_half = merge_sort(seq[:mid])
        right_half = merge_sort(seq[mid:])
        new_seq = merge_sort_list(left_half, right_half)
        return new_seq

if __name__ == '__main__':
    seq = [1, 49, 9, 10, 23, 4, 2, 5]
    result = merge_sort(seq)
    print(result)