https://leetcode.com/problems/next-closest-time/ - https://leetcode.com/submissions/detail/275603804/

next-closest-time.py

class Solution:
  # Suitable ranges for:
  # - HH is 00 to 23
  # - MM is 00 to 59

  def num_to_digits(self, n):
    s = list(map(int, list(str(n))))
    if n < 10:
      return [0, s[0]]
    return s

  def is_ok(self, ns):
    for n in ns:
      if n not in self.nums:
        return False
    return True

  # Returns (m: int, reset: bool)
  def next_group(self, m, lower, upper):
    for m in range(m+1, upper):
      if self.is_ok(self.num_to_digits(m)):
        return (m, False)
      
    # Now we have to find the smallest possible at all
    for m in range(lower, upper):
      if self.is_ok(self.num_to_digits(m)):
        return (m, True)

  def nextClosestTime(self, time: str) -> str:
    # Remove :
    time = time.replace(":", "")

    hrs = int(time[:2])
    mins = int(time[2:])

    # Produce a list of integers
    time = list(map(int, list(time)))

    # Sort the numbers
    self.nums = sorted(time)

    mins, force = self.next_group(mins, 0, 60)
    if force:
      hrs, force = self.next_group(hrs, 0, 24)
    return "{:02d}:{:02d}".format(hrs, mins)