Latest Time by Replacing Hidden Digits

This approach involves iterating through all possible valid times in a day, from the latest (23:59) to the earliest (00:00). For each time, we check if it can be formed from the input pattern. The first time that matches the pattern is the answer, as we are iterating downwards.

• Loop for hour from 23 down to 0.
• Inside this loop, loop for minute from 59 down to 0.
• Format the current hour and minute into a hh:mm string. For example, if hour is 9 and minute is 5, the string is "09:05".
• Create a boolean flag match and set it to true.
• Compare this formatted time string with the input time string character by character.
• A generated time is a "match" if for every position i, either generated_time[i] == input_time[i] or input_time[i] == '?'.
• If match is still true after all checks, we have found the latest possible time. Return the formatted time string.

We can systematically check every minute of the day, starting from 23:59 and going down to 00:00. For each time (e.g., "23:59"), we create its string representation. We then compare this generated time string with the input time string character by character. A generated time is a "match" if for every position i from 0 to 4, either generated_time.charAt(i) == time.charAt(i) or time.charAt(i) == '?'. Since we are iterating from the latest possible time downwards, the very first match we find will be the latest valid time that can be formed. The problem guarantees that a valid time can always be produced, so we are sure to find a match.

class Solution {
    public String latestTimeByReplacingHiddenDigits(String time) {
        for (int h = 23; h >= 0; h--) {
            for (int m = 59; m >= 0; m--) {
                String currentTime = String.format("%02d:%02d", h, m);
                if (matches(currentTime, time)) {
                    return currentTime;
                }
            }
        }
        return ""; // Should not be reached based on problem constraints
    }

    private boolean matches(String currentTime, String pattern) {
        for (int i = 0; i < 5; i++) {
            if (pattern.charAt(i) != '?' && pattern.charAt(i) != currentTime.charAt(i)) {
                return false;
            }
        }
        return true;
    }
}