LeetCode 1736. Latest Time by Replacing Hidden Digits Solution in Java, C++, Python & More | Explanation + Code

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.

Solutions

Solution 1: Greedy

We process each digit of the string in order, following these rules:

1. First digit: If the value of the second digit is determined and falls within the range [4, 9], then the first digit can only be 1. Otherwise, the first digit can be up to 2.
2. Second digit: If the value of the first digit is determined and is 2, then the second digit can be up to 3. Otherwise, the second digit can be up to 9.
3. Third digit: The third digit can be up to 5.
4. Fourth digit: The fourth digit can be up to 9.

The time complexity is O(1), and the space complexity is O(1).

PythonJavaC++GoJavaScript

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)(code-box)

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); } }(code-box)

class Solution { public: string maximumTime(string time) { if (time[0] == '?') { time[0] = (time[1] >= '4' && time[1] <= '9') ? '1' : '2'; } if (time[1] == '?') { time[1] = (time[0] == '2') ? '3' : '9'; } if (time[3] == '?') { time[3] = '5'; } if (time[4] == '?') { time[4] = '9'; } return time; } };(code-box)

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) }(code-box)

/** * @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(''); };(code-box)