Introduction

In this blog post, we will explore how to solve the LeetCode problem "2437" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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.

Explanation

Here's the breakdown of the approach and the Python code:

• Analyze the Constraints: The problem restricts hours to 00-23 and minutes to 00-59. This is critical for calculating valid combinations when question marks exist.
• Conditional Logic: We use if/else statements to check different patterns of '?' in the input string and calculate the possible valid combinations based on those patterns.

• Calculate combinations of the HH and MM sections: Calculate the possible valid combinations for the 'HH' section and 'MM' section independently and multiply them to get the total valid clock times.

• Runtime Complexity: O(1), Storage Complexity: O(1)

Code

    def countTime(time):
    h1 = time[0]
    h2 = time[1]
    m1 = time[3]
    m2 = time[4]

    hours = 0
    minutes = 0

    if h1 == '?' and h2 == '?':
        hours = 24
    elif h1 == '?':
        if int(h2) <= 3:
            hours = 3
        else:
            hours = 2
    elif h2 == '?':
        if int(h1) == 0 or int(h1) == 1:
            hours = 10
        else:
            hours = 4
    else:
        hours = 1

    if m1 == '?' and m2 == '?':
        minutes = 60
    elif m1 == '?':
        minutes = 6
    elif m2 == '?':
        minutes = 10
    else:
        minutes = 1

    return hours * minutes