题目85 五键键盘--python

choose = ''
screen = ''
board = ''
for i in range(len(s)):
    if s[i] == '1':
        if choose == '':
            screen += 'A'
        else:
            choose = ''
            screen = 'A'
    elif s[i] == '2':
        board = choose
    elif s[i] == '3':
        board =choose
        choose = ''
    elif s[i] == '4':
        if choose != '':
            screen = board
            choose = ''
        else:
            screen += board
    elif s[i] == '5':
        choose = screen
print(len(screen))