[Level 2] 큰 수 만들기

def solution(number, k):
    answer = []
    for num in number:
        while len(answer) > 0 and k > 0 and answer[-1] < num:
            answer.pop()
            k -= 1
        answer.append(num)
    if k != 0:
        answer = answer[:-k]
    return ''.join(answer)