Introduction

In this blog post, we will explore how to solve the LeetCode problem "1736" 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 time in the form of hh:mm, where some of the digits in the string are hidden (represented by ?). The valid times are those inclusively between 00:00 and 23:59. Return the latest valid time you can get from time by replacing the hidden digits. Example 1: Input: time = "2?:?0" Output: "23:50" Explanation: The latest hour beginning with the digit '2' is 23 and the latest minute ending with the digit '0' is 50. Example 2: Input: time = "0?:3?" Output: "09:39" Example 3: Input: time = "1?:22" Output: "19:22" Constraints: time is in the format hh:mm. It is guaranteed that you can produce a valid time from the given string.

Explanation

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

• High-Level Approach:

  • Iterate through the time string, focusing on the ? characters.
  • Replace each ? with the largest possible digit that results in a valid time, considering the constraints for hours (00-23) and minutes (00-59).
  • Perform the replacements in the order: hours digit 1, hours digit 2, minutes digit 1, minutes digit 2.

• Complexity:

  • Runtime Complexity: O(1) - The solution involves a fixed number of checks and replacements. The length of the input string is constant.
  • Storage Complexity: O(1) - The solution uses a constant amount of extra space.

Code

    def maximum_time(time: str) -> str:
    """
    Finds the latest valid time you can get from time by replacing the hidden digits.
    """
    time_list = list(time)

    # Fill in the hours
    if time_list[0] == '?' and time_list[1] == '?':
        time_list[0] = '2'
        time_list[1] = '3'
    elif time_list[0] == '?':
        if time_list[1] <= '3':
            time_list[0] = '2'
        else:
            time_list[0] = '1'
    elif time_list[1] == '?':
        if time_list[0] == '2':
            time_list[1] = '3'
        else:
            time_list[1] = '9'

    # Fill in the minutes
    if time_list[3] == '?':
        time_list[3] = '5'
    if time_list[4] == '?':
        time_list[4] = '9'

    return "".join(time_list)