Leetcode2437. 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: 2Explanation: 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: 100Explanation: Each ? can be replaced by any digit from 0 to 9, so we have 100 total choices.

Example 3:

Input: time = "??:??"Output: 1440Explanation: 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.

• 难度等级：Easy
  

只要知道小时的可能性跟分钟的可能是单独即可，

先去判断小时的可能性，如果2个都是？，是多少个，如果第1个是？，多少个，如果第2个是？，多少个，同理判断分钟的可能性；

最后返回小时跟分钟可能性的乘积即可。

Runtime0 ms

Beats

100%

Memory39.8 MB

Beats

94.41%

Click to check the distribution chart