681. Next Closet Time

Given a time represented in the format "HH:MM", form the next closest time by reusing the current digits. There is no limit on how many times a digit can be reused.

You may assume the given input string is always valid. For example, "01:34", "12:09" are all valid. "1:34", "12:9" are all invalid.

Example 1:

Input:
 "19:34"

Output:
 "19:39"

Explanation:
 The next closest time choosing from digits 1, 9, 3, 4, is 19:39, which occurs 5 minutes later.  It is not 19:33, 
 because this occurs 23 hours and 59 minutes later.

Example 2:

Input:
 "23:59"

Output:
 "22:22"

Explanation:
 The next closest time choosing from digits 2, 3, 5, 9, is 22:22. 
 It may be assumed that the returned time is next day's time since it is smaller than the input time numerically.

Thoughts:

1. Brutally find all the digits increments (24*60), rank the time

2. Using time increments to find the closest time

class Solution(object):
    def nextClosestTime(self, time):
        """
        :type time: str
        :rtype: str
        """
        # turn the forward by one minute until time follows the same set
        return min((t <= time, t)
               for i in range(24 * 60)
               for t in ['%02d:%02d' % divmod(i, 60)]
               if set(t) <= set(time)) [1];