# Validating traditional time formats using Regular Expression

• Last Updated : 22 Dec, 2022

Given a string Time Format, the task is to check whether the string follows the time formats “HH: MM: SS” or “HH: MM” using Regular Expression. Rules for valid time formats:

• It should contain only digits[0-9] and colon (:).
• No alphabets are allowed or any special characters.

Examples:

Input: “12: 55”
Output: True

Input: “24: 12: 12”
Output: False
Explanation: The standard time is never expressed 24:00:00 hours or anything else after that.

Approach: The problem can be solved based on the following idea:

Create a regex pattern to validate the number as written below:
regex= ^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9](?::[0-5]?[0-9])?\$

^ : Beginning of the string
?: : not compulsion to be present
[01] : indicates either 1 or 0
[0 – 9] : any one digit from 0 to 9 should be present.
\ : either first part before ” or second part after ”.

Follow the below steps to implement the idea:

• Create regex expression for Time formats.
• Use Pattern class to compile the regex formed.
•  Use the matcher function to check whether the Time format is valid or not.
• If it is valid, return true. Otherwise, return false.

Below is the implementation of the above approach.

## C++

```// C++ program to validate the
// Traditional Time Formats (HH:MM:SS  or HH:MM)
// using RegularExpression

#include <bits/stdc++.h>
#include <regex>
using namespace std;

// Function to validate the
// Traditional Time Formats (HH:MM:SS  or HH:MM)
string isValidTime(string str)
{
// Regex to check valid
// Traditional Time Formats
// (HH:MM:SS  or HH:MM).
const regex pattern("^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9]"
"(?::[0-5]?[0-9])?\$");

// If the str
// is empty return false
if (str.empty()) {
return "false";
}

// Return true if the str
// matched the ReGex
if (regex_match(str, pattern)) {
return "true";
}
else {
return "false";
}
}

// Driver Code
int main()
{
// Test Case 1:
string str1 = "23:01:00";
cout << isValidTime(str1) << endl;

// Test Case 2:
string str2 = "12:59:00";
cout << isValidTime(str2) << endl;

// Test Case 3:
string str3 = "19:00:59";
cout << isValidTime(str3) << endl;

// Test Case 4:
string str4 = "19:00:96";
cout << isValidTime(str4) << endl;

// Test Case 5:
string str5 = "08:78:70";
cout << isValidTime(str5) << endl;

// Test Case 6:
string str6 = "00:98:00";
cout << isValidTime(str6) << endl;

return 0;
}```

## Java

```// Java code to implement the approach

import java.util.regex.*;

class GFG {

// Function to validate the
// Traditional Time Formats
// (HH:MM:SS  or HH:MM)
public static boolean isValidTime(String str)
{
// Regex to check valid Time
String regex
= "^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9](?::[0-5]?[0-9])?\$";

// Compile the ReGex
Pattern p = Pattern.compile(regex);

// If the str
// is empty return false
if (str == null) {
return false;
}

// Pattern class contains matcher()
// method to find matching between
// given str using regex.
Matcher m = p.matcher(str);

// Return if the str
// matched the ReGex
return m.matches();
}

// Driver Code.
public static void main(String args[])
{
// Test Case 1:
String str1 = "23:10:59";
System.out.println(isValidTime(str1));

// Test Case 2:
String str2 = "12:59:00";
System.out.println(isValidTime(str2));

// Test Case 3:
String str3 = "19:00:59";
System.out.println(isValidTime(str3));

// Test Case 4:
String str4 = "19:00:96";
System.out.println(isValidTime(str4));

// Test Case 5:
String str5 = "08:78:70";
System.out.println(isValidTime(str5));

// Test Case 6:
String str6 = "00:98:00";
System.out.println(isValidTime(str6));
}
}```

## Python3

```# Python3 program to validate
# Traditional Time Formats (HH:MM:SS  or HH:MM)
# using Regular Expression

import re

# Function to validate
# Traditional Time Formats (HH:MM:SS  or HH:MM)
def isValidTime(str):

# Regex to check valid time
regex = "^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9](?::[0-5]?[0-9])?\$"

# Compile the ReGex
p = re.compile(regex)

# If the string is empty
# return false
if (str == None):
return "false"

# Return if the string
# matched the ReGex
if(re.search(p, str)):
return "true"
else:
return "false"

# Driver code
if __name__ == '__main__':

# Test Case 1:
str1 = "23:01:00"
print(isValidTime(str1))

# Test Case 2:
str2 = "12:59:00"
print(isValidTime(str2))

# Test Case 3:
str3 = "19:00:59"
print(isValidTime(str3))

# Test Case 4:
str4 = "19:00:96"
print(isValidTime(str4))

# Test Case 5:
str5 = "08:78:70"
print(isValidTime(str5))

# Test Case 6:
str6 = "00:98:00"
print(isValidTime(str6))
```

## C#

```// Include namespace system
using System;
using System.Text.RegularExpressions;

public class GFG
{

// Function to validate the
// Traditional Time Formats
// (HH:MM:SS  or HH:MM)
public static bool isValidTime(String str)
{

// Regex to check valid LEI Code
var regex = new Regex("^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9](?::[0-5]?[0-9])?\$");

// If the str
// is empty return false
if (str == null)
{
return false;
}

// Pattern class contains matcher()
// method to find matching between
// given LEI Code using regex.
var m = regex.Match(str);

// Return if the MICR Code
// matched the ReGex
return m.Success;
}

// Driver Code.
public static void Main(String[] args)
{

// Test Case 1:
var str1 = "23:10:59";
Console.WriteLine(GFG.isValidTime(str1));

// Test Case 2:
var str2 = "12:59:00";
Console.WriteLine(GFG.isValidTime(str2));

// Test Case 3:
var str3 = "19:00:59";
Console.WriteLine(GFG.isValidTime(str3));

// Test Case 4:
var str4 = "19:00:96";
Console.WriteLine(GFG.isValidTime(str4));

// Test Case 5:
var str5 = "08:78:70";
Console.WriteLine(GFG.isValidTime(str5));

// Test Case 6:
var str6 = "00:98:00";
Console.WriteLine(GFG.isValidTime(str6));
}
}

// This code is contributed by Potta Lokesh.```

## Javascript

```// Javascript program to validate
// Traditional Time Formats (HH:MM:SS  or HH:MM)
//using Regular Expression

// Function to validate the
// Traditional Time Formats (HH:MM:SS  or HH:MM)
function isValidTime(str) {
// Regex to check valid
// Traditional Time Formats (HH:MM:SS  or HH:MM)
let regex = new RegExp(/^(?:[01]?[0-9]|2[0-3]):[0-5]?[0-9](?::[0-5]?[0-9])?\$/);

// 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 = "23:01:00";
console.log(isValidTime(str1));

// Test Case 2:
let str2 = "12:59:00";
console.log(isValidTime(str2));

// Test Case 3:
let str3 = "19:00:59";
console.log(isValidTime(str3));

// Test Case 4:
let str4 = "19:00:96";
console.log(isValidTime(str4));

// Test Case 5:
let str5 = "08:78:70";
console.log(isValidTime(str5));

// Test Case 6:
let str6 = "00:98:00";
console.log(isValidTime(str6));

```
Output

```true
true
true
false
false
false```

Time Complexity: O(N) for each testcase, where N is the length of the given string.
Auxiliary Space: O(1)

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