Formatted question description: https://leetcode.ca/all/1736.html

# 1736. Latest Time by Replacing Hidden Digits

Easy

## Description

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.

## Solution

First consider the hour. The hour must be in range [00, 23]. Replace the hidden digits with the maximum possible value in the range. Then consider the minute. The minute must be in range [00, 59]. The two digits of the minute should be replaced with the maximum possible digit, which are 5 and 9 respectively. Finally, return the replaced time.

class Solution {
public String maximumTime(String time) {
char[] array = time.toCharArray();
if (array[0] == '?') {
if (array[1] == '?') {
array[0] = '2';
array[1] = '3';
} else {
if (array[1] <= '3')
array[0] = '2';
else
array[0] = '1';
}
}
if (array[1] == '?') {
if (array[0] == '2')
array[1] = '3';
else
array[1] = '9';
}
if (array[3] == '?')
array[3] = '5';
if (array[4] == '?')
array[4] = '9';
return new String(array);
}
}