README.md

2437. Number of Valid Clock Times

You are given a string of length 5 called time, representing the current time on a digital clock in the format "hh:mm". The earliest possible time is "00:00" and the latest possible time is "23:59".

In the string time, the digits represented by the ? symbol are unknown, and must be replaced with a digit from 0 to 9.

Return an integer answer, the number of valid clock times that can be created by replacing every ? with a digit from 0 to 9.

Example 1:

Input: time = "?5:00"
Output: 2
Explanation: We can replace the ? with either a 0 or 1, producing "05:00" or "15:00". Note that we cannot replace it with a 2, since the time "25:00" is invalid. In total, we have two choices.

Example 2:

Input: time = "0?:0?"
Output: 100
Explanation: Each ? can be replaced by any digit from 0 to 9, so we have 100 total choices.

Example 3:

Input: time = "??:??"
Output: 1440
Explanation: There are 24 possible choices for the hours, and 60 possible choices for the minutes. In total, we have 24 * 60 = 1440 choices.

Constraints:

• time is a valid string of length 5 in the format "hh:mm".
• "00" <= hh <= "23"
• "00" <= mm <= "59"
• Some of the digits might be replaced with '?' and need to be replaced with digits from 0 to 9.

Solutions (Python)

1. Solution

class Solution:
    def countTime(self, time: str) -> int:
        ret = 1

        if time[0] == '?' and time[1] == '?':
            ret *= 24
        elif time[0] == '?':
            ret *= 3 if time[1] < '4' else 2
        elif time[1] == '?':
            ret *= 10 if time[0] < '2' else 4
        ret *= 6 if time[3] == '?' else 1
        ret *= 10 if time[4] == '?' else 1

        return ret