프로그래머스 - 택배상자 (L2)

 1def solution(order):
 2    answer = 0
 3    length = len(order)
 4    stackA = [i for i in range(length, 0, -1)]
 5    stackB = []
 6    
 7    for i in order:
 8        while True:
 9            if stackA and stackA[-1] == i:
10                stackA.pop()
11                break
12            if stackB and stackB[-1] == i:
13                stackB.pop()
14                break
15
16            if stackB and stackB[-1] > i:
17                return answer
18            
19            stackB.append(stackA.pop())
20        answer += 1
21        
22    return answer