LatestTimeByReplacingHiddenDigits.cpp

// Source : https://leetcode.com/problems/latest-time-by-replacing-hidden-digits/
// Author : Hao Chen
// Date   : 2021-03-27

/***************************************************************************************************** 
 *
 * 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.
 ******************************************************************************************************/

class Solution {
public:
    string maximumTime(string time) {
        
        if (time[0] == '?' ) {
            time[0] = (time[1] == '?' || time[1] < '4') ?  '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;
    }
};