问代码Vita:在HH:MM:SS格式中，使用九个给定的个位数中的任意六个，形成最大可能的时间

EN

def placewise_max(max_template, pool):
    """
    Try to form the lexicographically greatest string from the characters in
    the pool, where the character in each position of the output does not
    exceed the character at the corresponding position in the template.
    Return the empty string if any position cannot be filled.

    >>> placewise_max('91210', list('02301'))
    '31200'
    >>> placewise_max('elmo', 'abcdefghijklm')
    'elmk'
    >>> placewise_max('elmo', 'limo')
    ''
    """
    pool = sorted(pool, reverse=True)
    output = []
    try:
        for t in max_template:
            char = next(c for c in iter(pool) if c <= t)
            pool.remove(char)
            output.append(char)
        return ''.join(output)
    except StopIteration:   # next() failed to pick from the pool
        return ''

def max_time(digits):
    best = max(
        placewise_max('240000', digits),
        placewise_max('235959', digits),
        placewise_max('195959', digits)
    )
    if best and (best != '000000'):
        return '{0}{1}:{2}{3}:{4}{5}'.format(*best)

if __name__ == '__main__':
    print(max_time(input().split(',')) or 'Impossible')

import itertools
from datetime import datetime

inp = [0,9,5,5,5,5,5,5,5]

form = "%H:%M:%S"
possible = False
max_time = datetime.strptime("00:00:00", form).time()
for perm in itertools.permutations(inp, 6):
    time_string = "%d%d:%d%d:%d%d" % perm
    try:
        time_object = datetime.strptime(time_string, form).time()
        possible = True
        max_time = max(time_object, max_time)
    except: pass

if possible:
    print(max_time)
else:
    print("Impossible")