Open in App
Not now

# Validate week days using Regular Expression

• Last Updated : 22 Dec, 2022

Given some Weekdays, the task is to check if they are valid or not using regular expressions.

Rules for the valid Weekdays :

• It should contain specific only words as a string. They are mentioned below:
• Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, and Sunday.
• Mon, Tues, Wed, Thurs, Fri, Sat, Sun.
• Mon., Tues., Wed., Thurs., Fri., Sat., Sun.
• mon, tues, wed, thurs, fri, sat, sun.

Examples:

Input: “Monday”
Output: True

Input: Payday
Output: False

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

Create a regex pattern to validate the number as written below:
regex= ^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|fri)(day|\.)?\$|wed(\.|nesday)?\$|Wed(\.|nesday)?\$|Sat(\.|urday)?\$|sat(\.|urday)?\$|t((ue?)|(hu?r?))\.?\$|T((ue?)|(hu?r?))\.?\$

Where,

• ^ : This indicates the start of the string.
• \$ :End of the string.
• | : OR

Follow the below steps to implement the idea:

• Create a regex expression for Weekdays.
• Use Pattern class to compile the regex formed.
• Use the matcher function to check whether the Weekday 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
// Weekday using Regular
// Expression

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

// Function to validate the
// Weekday
string isValid_WeekDay(string str)
{
// Regex to check valid weekday
const regex pattern(
"^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|"
"fri)(day|\.)?\$|wed(\.|nesday)?\$|Wed(\.|nesday)?\$|"
"Sat(\.|urday)?\$|sat(\.|urday)?\$|t((ue?)|(hu?r?))"
"\.?\$|T((ue?)|(hu?r?))\.?\$");

// 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 = "Sunday";
cout << isValid_WeekDay(str1) << endl;

// Test Case 2:
string str2 = "Monday";
cout << isValid_WeekDay(str2) << endl;

// Test Case 3:
string str3 = "Tues.";
cout << isValid_WeekDay(str3) << endl;

// Test Case 4:
string str4 = "Payday";
cout << isValid_WeekDay(str4) << endl;

// Test Case 5:
string str5 = "Friday";
cout << isValid_WeekDay(str5) << endl;

// Test Case 6:
string str6 = "Birthday";
cout << isValid_WeekDay(str6) << endl;

return 0;
}```

## Java

```// Java program to validate the
// Weekday using Regular Expression

import java.util.regex.*;

class GFG {
// Function to validate the
// Weekday
public static boolean isValid_WeekDay(String str)
{

// Regex to check valid weekday
String regex
= "^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|fri)(day|\\.)"
+ "?\$|wed(\\.|nesday)?\$|Wed(\\.|nesday)?\$|Sat(\\.|urday)"
+ "?\$|sat(\\.|urday)?\$|t((ue?)|(hu?r?))\\.?\$|T((ue?)|(hu?r?))\\.?\$";

// 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 = "Sunday";
System.out.println(isValid_WeekDay(str1));

// Test Case 2:
String str2 = "Monday";
System.out.println(isValid_WeekDay(str2));

// Test Case 3:
String str3 = "Tues.";
System.out.println(isValid_WeekDay(str3));

// Test Case 4:
String str4 = "Payday";
System.out.println(isValid_WeekDay(str4));

// Test Case 5:
String str5 = "Friday";
System.out.println(isValid_WeekDay(str5));

// Test Case 6:
String str6 = "Birthday";
System.out.println(isValid_WeekDay(str6));
}
}```

## Python3

```# Python3 program to validate
# Weekday using Regular Expression

import re

# Function to validate
# Weekday

def isValid_WeekDay(str):

# Regex to check valid Weekday
regex = "^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|fri)(day|\.)"\
"?\$|wed(\.|nesday)?\$|Wed(\.|nesday)?\$|Sat(\.|urday)?\$|sat(\.|urday)"\
"?\$|t((ue?)|(hu?r?))\.?\$|T((ue?)|(hu?r?))\.?\$"

# 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 = "Sunday"
print(isValid_WeekDay(str1))

# Test Case 2:
str2 = "Monday"
print(isValid_WeekDay(str2))

# Test Case 3:
str3 = "Tues."
print(isValid_WeekDay(str3))

# Test Case 4:
str4 = "Payday"
print(isValid_WeekDay(str4))

# Test Case 5:
str5 = "Friday"
print(isValid_WeekDay(str5))

# Test Case 6:
str6 = "Birthday"
print(isValid_WeekDay(str6))
```

## C#

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

public class GFG
{

// Function to validate the
// Weekday
public static bool isValid_WeekDay(String str)
{

// Regex to check valid LEI Code
var regex = new Regex("^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|fri)(day|\\.)"
+ "?\$|wed(\\.|nesday)?\$|Wed(\\.|nesday)?\$|Sat(\\.|urday)"
+ "?\$|sat(\\.|urday)?\$|t((ue?)|(hu?r?))\\.?\$|T((ue?)|(hu?r?))\\.?\$");

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

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

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

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

// Test Case 1:
var str1 = "Sunday";
Console.WriteLine(GFG.isValid_WeekDay(str1));

// Test Case 2:
var str2 = "Monday";
Console.WriteLine(GFG.isValid_WeekDay(str2));

// Test Case 3:
var str3 = "Tues.";
Console.WriteLine(GFG.isValid_WeekDay(str3));

// Test Case 4:
var str4 = "Payday";
Console.WriteLine(GFG.isValid_WeekDay(str4));

// Test Case 5:
var str5 = "Friday";
Console.WriteLine(GFG.isValid_WeekDay(str5));

// Test Case 6:
var str6 = "Birthday";
Console.WriteLine(GFG.isValid_WeekDay(str6));
}
}

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

## Javascript

```// Javascript program to validate
// Weekday using Regular Expression

// Function to validate the
// Weekday
function isValid_WeekDay(str) {
// Regex to check valid
// weekday
let regex = new RegExp(/^(sun|Sun|mon|Mon|t(ues|hurs)|(T(ues|hurs))|Fri|fri)(day|\.)?\$|wed(\.|nesday)?\$|Wed(\.|nesday)?\$|Sat(\.|urday)?\$|sat(\.|urday)?\$|t((ue?)|(hu?r?))\.?\$|T((ue?)|(hu?r?))\.?\$/);

//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 = "Sunday";
console.log(isValid_WeekDay(str1));

// Test Case 2:
let str2 = "Monday";
console.log(isValid_WeekDay(str2));

// Test Case 3:
let str3 = "Tues.";
console.log(isValid_WeekDay(str3));

// Test Case 4:
let str4 = "Payday";
console.log(isValid_WeekDay(str4));

// Test Case 5:
let str5 = "Friday";
console.log(isValid_WeekDay(str5));

// Test Case 6:
let str6 = "Birthday";
console.log(isValid_WeekDay(str6));
```
Output

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

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

Related Articles:

My Personal Notes arrow_drop_up
Related Articles