Latest Time You Can Obtain After Replacing Characters

Quick Links

Problem Description

Ah, the classic dilemma of time management! Imagine you’re late for a meeting, and your watch is playing hide-and-seek with the digits. The problem, “Latest Time You Can Obtain After Replacing Characters,” is like that moment when you realize your clock has more question marks than actual numbers.

In this LeetCode challenge, you’re given a string representing a time in the format “HH:MM,” where some digits might be replaced with question marks. Your mission, should you choose to accept it, is to replace those question marks with digits to create the latest possible valid time.

For example, if your time is “2?:3?”, you could replace it with “23:59” because, let’s be honest, who wouldn’t want to stretch their time to the max?

Code Solution


class Solution:
    def findLatestTime(self, s: str) -> str:
        ans = list(s)
        if s[0] == '?':
            ans[0] = '1' if s[1] == '?' or s[1] < '2' else '0'
        if s[1] == '?':
            ans[1] = '1' if ans[0] == '1' else '9'
        if s[3] == '?':
            ans[3] = '5'
        if s[4] == '?':
            ans[4] = '9'
        return ''.join(ans)

Approach

The approach here is as straightforward as a GPS telling you to "turn left." The code checks each position in the time string and replaces the question marks with the highest possible digits that still form a valid time.

Hour Handling: If the first digit is a question mark, it checks the second digit to decide whether to set it to '1' or '0'.
Minute Handling: For the minutes, it ensures that the maximum valid digits are used.
Final Assembly: Finally, it joins the list back into a string and returns the latest time.

Time and Space Complexity

Complexity Type	Complexity
Time Complexity	O(1) - The solution processes a fixed number of characters (5 in total).
Space Complexity	O(1) - The space used does not depend on the input size.

Real-World Example

Imagine you’re at a party, and the clock strikes 11:??. You know you can’t leave until you’ve had your fill of snacks and awkward small talk. You quickly replace the question marks to make it 11:59, maximizing your time to enjoy the festivities. Just like in our problem, you’re trying to squeeze every last second out of your evening!