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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);
}
}

############

class Solution {
public String maximumTime(String time) {
char[] t = time.toCharArray();
if (t[0] == '?') {
t[0] = t[1] >= '4' && t[1] <= '9' ? '1' : '2';
}
if (t[1] == '?') {
t[1] = t[0] == '2' ? '3' : '9';
}
if (t[3] == '?') {
t[3] = '5';
}
if (t[4] == '?') {
t[4] = '9';
}
return new String(t);
}
}

• // OJ: https://leetcode.com/problems/latest-time-by-replacing-hidden-digits/
// Time: O(1)
// Space: O(1)
class Solution {
public:
string maximumTime(string time) {
if (time[0] == '?') time[0] = time[1] == '?' || time[1] <= '3' ? '2' : '1';
if (time[1] == '?') time[1] = time[0] == '2' ? '3' : '9';
if (time[3] == '?') time[3] = '5';
if (time[4] == '?') time[4] = '9';
return time;
}
};

• class Solution:
def maximumTime(self, time: str) -> str:
t = list(time)
if t[0] == '?':
t[0] = '1' if '4' <= t[1] <= '9' else '2'
if t[1] == '?':
t[1] = '3' if t[0] == '2' else '9'
if t[3] == '?':
t[3] = '5'
if t[4] == '?':
t[4] = '9'
return ''.join(t)

############

# 1736. Latest Time by Replacing Hidden Digits
# https://leetcode.com/problems/latest-time-by-replacing-hidden-digits/

class Solution:
def maximumTime(self, time: str):
time = list(time)

if time[0] == "?":
if time[1] == "?" or int(time[1]) <= 3:
time[0] = "2"
else:
time[0] = "1"

if time[1] == "?":
if time[0] == "2":
time[1] = "3"
elif time[0] == "1":
time[1] = "9"
else:
time[1] = "9"

if time[3] == "?":
time[3] = "5"

if time[4] == "?":
time[4] = "9"

return "".join(time)


• func maximumTime(time string) string {
t := []byte(time)
if t[0] == '?' {
if t[1] >= '4' && t[1] <= '9' {
t[0] = '1'
} else {
t[0] = '2'
}
}
if t[1] == '?' {
if t[0] == '2' {
t[1] = '3'
} else {
t[1] = '9'
}
}
if t[3] == '?' {
t[3] = '5'
}
if t[4] == '?' {
t[4] = '9'
}
return string(t)
}

• /**
* @param {string} time
* @return {string}
*/
var maximumTime = function (time) {
const t = Array.from(time);
if (t[0] === '?') {
t[0] = t[1] >= '4' && t[1] <= '9' ? '1' : '2';
}
if (t[1] === '?') {
t[1] = t[0] == '2' ? '3' : '9';
}
if (t[3] === '?') {
t[3] = '5';
}
if (t[4] === '?') {
t[4] = '9';
}
return t.join('');
};