wall_build.py

import collections


def solution(H):
    result = 0
    queue = collections.deque()
    queue.append(H)
    # print(F"queue = {queue}")
    while queue:
        # print(queue)
        wall = queue.popleft()
        if 0 in wall:
            split_idx = wall.index(0)
            if wall[:split_idx]:
                queue.append(wall[:split_idx])
            if wall[split_idx+1:]:
                queue.append(wall[split_idx+1:])
            continue
        min_h = min(wall)
        result += 1
        wall = list(map(lambda x: x - min_h, wall))
        # print(F"wall = {wall}")
        queue.append(wall)
    return result


xs = [8, 8, 5, 7, 9, 8, 7, 4, 8]
# xs = [8, 8, 5, 7, 9, 0, 7, 4, 8]
print(F"solution(xs) = {solution(xs)}")