How to validate time in 24-hour format using Regular Expression
Given a string str, the task is to check whether the string is valid time in 24-hour format or not by using Regular Expression.
The valid time in the 24-hour format must satisfy the following conditions.
- It should start from 0-23 or 00-23.
- It should be followed by a ‘:'(colon).
- It should be followed by two digits from 00 to 59.
- It should not end with ‘am’, ‘pm’ or ‘AM’, ‘PM’.
Examples:
Input: str = “13:05”
Output: true
Explanation: The given string satisfies all the above mentioned conditions.Input: str = “02:15”
Output: true
Explanation: The given string satisfies all the above mentioned conditions.Input: str = “24:00”
Output: false
Explanation: The given string doesn’t be in the range of 0-23 or 00-23(i.e., hour is out of range), therefore it is not a valid time in 24-hour format.Input: str = “10:60”
Output: false
Explanation: The given string doesn’t be in the range of 00 to 59(i.e., minute is out of range), therefore it is not a valid time in 24-hour format.Input: str = “10:15 PM”
Output: false
Explanation: The given string end with ‘AM’ or ‘PM’, therefore it is not a valid time in 24-hour format.
Approach: This problem can be solved by using Regular Expressions.
- Get the string.
- Create a regular expression to check time in 24-hour format as mentioned below:
regex = "([01]?[0-9]|2[0-3]):[0-5][0-9]";
Where:
- ( represents the start of the group.
- [01]?[0-9] represents the time that starts with 0-9, 1-9, 00-09, 10-19.
- | represents or.
- 2[0-3] represents the time starting with 20-23.
- ) represents the end of the group.
- : represents the time that should be followed by a colon(:).
- [0-5][0-9] represents the time followed by 00 to 59
- Match the given string with the regex, in Java, this can be done by using Pattern.matcher().
- Return true if the string matches with the given regex, else return false.
Below is the implementation of the above approach:
C++
// C++ program to validate // time in 24-hour format // using Regular Expression #include <iostream> #include <regex> using namespace std; // Function to validate time in 24-hour format bool isValidTime(string str) { // Regex to check valid time in 24-hour format const regex pattern( "([01]?[0-9]|2[0-3]):[0-5][0-9]" ); // If the time in 24-hour format // is empty return false if (str.empty()) { return false ; } // Return true if the time in 24-hour format // matched the ReGex if (regex_match(str, pattern)) { return true ; } else { return false ; } } // Driver Code int main() { // Test Case 1: string str1 = "13:05" ; cout << str1 + ": " << isValidTime(str1) << endl; // Test Case 2: string str2 = "02:15" ; cout << str2 + ": " << isValidTime(str2) << endl; // Test Case 3: string str3 = "24:00" ; cout << str3 + ": " << isValidTime(str3) << endl; // Test Case 4: string str4 = "10:60" ; cout << str4 + ": " << isValidTime(str4) << endl; // Test Case 5: string str5 = "10:15 PM" ; cout << str5 + ": " << isValidTime(str5) << endl; return 0; } // This code is contributed by yuvraj_chandra |
Java
// Java program to validate the time in // 24-hour format using Regular Expression. import java.util.regex.*; class GFG { // Function to validate the time in 24-hour format public static boolean isValidTime(String time) { // Regex to check valid time in 24-hour format. String regex = "([01]?[0-9]|2[0-3]):[0-5][0-9]" ; // Compile the ReGex Pattern p = Pattern.compile(regex); // If the time is empty // return false if (time == null ) { return false ; } // Pattern class contains matcher() method // to find matching between given time // and regular expression. Matcher m = p.matcher(time); // Return if the time // matched the ReGex return m.matches(); } // Driver Code. public static void main(String args[]) { // Test Case 1: String str1 = "13:05" ; System.out.println(str1 + ": " + isValidTime(str1)); // Test Case 2: String str2 = "02:15" ; System.out.println(str2 + ": " + isValidTime(str2)); // Test Case 3: String str3 = "24:00" ; System.out.println(str3 + ": " + isValidTime(str3)); // Test Case 4: String str4 = "10:60" ; System.out.println(str4 + ": " + isValidTime(str4)); // Test Case 5: String str5 = "10:15 PM" ; System.out.println(str5 + ": " + isValidTime(str5)); } } |
Python3
# Python3 program to validate the time in # 24-hour format using Regular Expression. import re # Function to validate the time # in 24-hour format def isValidTime(time): # Regex to check valid time in 24-hour format. regex = "^([01]?[0-9]|2[0-3]):[0-5][0-9]$" ; # Compile the ReGex p = re. compile (regex); # If the time is empty # return false if (time = = "") : return False ; # Pattern class contains matcher() method # to find matching between given time # and regular expression. m = re.search(p, time); # Return True if the time # matched the ReGex otherwise False if m is None : return False ; else : return True # Driver Code. if __name__ = = "__main__" : # Test Case 1: str1 = "13:05" ; print (str1, ": " , isValidTime(str1)); # Test Case 2: str2 = "02:15" ; print (str2, ": " , isValidTime(str2)); # Test Case 3: str3 = "24:00" ; print (str3, ": " , isValidTime(str3)); # Test Case 4: str4 = "10:60" ; print (str4, ": " , isValidTime(str4)); # Test Case 5: str5 = "10:15 PM" ; print (str5, ": " , isValidTime(str5)); # This code is contributed by AnkitRai01 |
C#
// C# program to validate the // Time in 24-hour format //using Regular Expressions using System; using System.Text.RegularExpressions; class GFG { // Main Method static void Main( string [] args) { // Input strings to Match // Time in 24-hour format string [] str={ "13:05" , "02:15" , "24:00" , "10:60" , "10:15 PM" }; foreach ( string s in str) { Console.WriteLine( isValidTime(s) ? "true" : "false" ); } Console.ReadKey(); } // method containing the regex public static bool isValidTime( string str) { string strRegex = @"^([01]?[0-9]|2[0-3]):[0-5][0-9]$" ; Regex re = new Regex(strRegex); if (re.IsMatch(str)) return ( true ); else return ( false ); } } // This code is contributed by Rahul Chauhan |
Javascript
// Javascript program to validate the time in // 24-hour format using Regular Expression. // Function to validate the // time in // 24-hour format function isValidTime(str) { // Regex to check valid // time in 24-hour format let regex = new RegExp(/^([01]\d|2[0-3]):?([0-5]\d)$/); // if str // is empty return false if (str == null ) { return "false" ; } // Return true if the str // matched the ReGex if (regex.test(str) == true ) { return "true" ; } else { return "false" ; } } // Driver Code // Test Case 1: let str1 = "13:05" ; console.log(isValidTime(str1)); // Test Case 2: let str2 = "02:15" ; console.log(isValidTime(str2)); // Test Case 3: let str3 = "24:00" ; console.log(isValidTime(str3)); // Test Case 4: let str4 = "10:60" ; console.log(isValidTime(str4)); // Test Case 5: let str5 = "10:15 PM" ; console.log(isValidTime(str5)); // This code is contributed by Rahul Chauhan |
13:05: true 02:15: true 24:00: false 10:60: false 10:15 PM: false
Time Complexity: O(N) for each test case, where N is the length of the given string.
Auxiliary Space: O(1)
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