Last Updated : 27 Dec, 2023
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Given some Phone Numbers, the task is to check if they are valid or not using regular expressions. Rules for the valid phone numbers are:
- The numbers should start with a plus sign ( + )
- It should be followed by Country code and National number.
- It may contain white spaces or a hyphen ( – ).
- the length of phone numbers may vary from 7 digits to 15 digits.
Examples:
Input:+91 (976) 006-4000
Output: TrueInput: +403 58 59594
Output: True
Approach: The problem can be solved based on the following idea:
Create a regex pattern to validate the number as written below:
regex= “^[+]{1}(?:[0-9\-\(\)\/\.]\s?){6, 15}[0-9]{1}$”
Where,
^ : start of the string
- [+]{1} :Matches a “+” character, matches exactly one of the preceding item
- (?:): :Groups multiple tokens together without creating a capture group.
- [0-9\-\(\)\/\.] : matches any character in the set from 0 to 9, “-“, “(“, “)”, “/”, and “.” .
- \\s : match a white space character
- ? : matches 0 or 1 of the preceding item.
- {6, 14} : This expression will match 6 to 14 of the preceding item.
- [0-9] : This will match values from 0 to 9
- {1} : This expression will match exactly one of the preceding item.
- $ : End of the string.
Follow the below steps to implement the idea:
- Create a regex expression for phone numbers.
- Use Pattern class to compile the regex formed.
- Use the matcher function to check whether the Phone Number is valid or not.
- If it is valid, return true. Otherwise, return false.
Below is the implementation of the above approach:
C++
#include <bits/stdc++.h>
#include <regex>
using namespace std;
// Function to validate the
// International Phone Numbers
string isValidPhoneNumber(string phonenumber)
{
// Regex to check valid phonenumber.
const regex pattern("^[+]{1}(?:[0-9\\-\\(\\)\\/"
"\\.]\\s?){6,15}[0-9]{1}$");
// If the phone number is empty return false
if (phonenumber.empty()) {
return "false";
}
// Return true if the phonenumber
// matched the ReGex
if (regex_match(phonenumber, pattern)) {
return "true";
}
else {
return "false";
}
}
// Driver Code
int main()
{
// Test Case 1:
string str1 = "+919136812895";
cout << isValidPhoneNumber(str1) << endl;
// Test Case 2:
string str2 = "+91 9136812895";
cout << isValidPhoneNumber(str2) << endl;
// Test Case 3:
string str3 = "+123 123456";
cout << isValidPhoneNumber(str3) << endl;
// Test Case 4:
string str4 = "654294563";
cout << isValidPhoneNumber(str4) << endl;
return 0;
}
Java
import java.util.regex.*;
public class PhoneNumberValidator {
// Function to validate the International Phone Numbers
static String isValidPhoneNumber(String phoneNumber) {
// Regex to check valid phone number.
String pattern = "^[+]{1}(?:[0-9\\-\\(\\)\\/" +
"\\.]\\s?){6,15}[0-9]{1}$";
// If the phone number is empty return false
if (phoneNumber.isEmpty()) {
return "false";
}
// Return true if the phone number
// matched the Regex
if (Pattern.matches(pattern, phoneNumber)) {
return "true";
} else {
return "false";
}
}
// Driver Code
public static void main(String[] args) {
// Test Case 1:
String str1 = "+919136812895";
System.out.println(isValidPhoneNumber(str1));
// Test Case 2:
String str2 = "+91 9136812895";
System.out.println(isValidPhoneNumber(str2));
// Test Case 3:
String str3 = "+123 123456";
System.out.println(isValidPhoneNumber(str3));
// Test Case 4:
String str4 = "654294563";
System.out.println(isValidPhoneNumber(str4));
}
}
Python3
import re
# Function to validate the International Phone Numbers
def is_valid_phone_number(phone_number):
# Regex to check valid phone number.
pattern = r"^[+]{1}(?:[0-9\\-\\(\\)\\/" \
"\\.]\\s?){6,15}[0-9]{1}$"
# If the phone number is empty return false
if not phone_number:
return "false"
# Return true if the phone number
# matched the Regex
if re.match(pattern, phone_number):
return "true"
else:
return "false"
# Driver Code
# Test Case 1:
str1 = "+919136812895"
print(is_valid_phone_number(str1))
# Test Case 2:
str2 = "+91 9136812895"
print(is_valid_phone_number(str2))
# Test Case 3:
str3 = "+123 123456"
print(is_valid_phone_number(str3))
# Test Case 4:
str4 = "654294563"
print(is_valid_phone_number(str4))
C#
using System;
using System.Text.RegularExpressions;
class Program
{
// Function to validate the International Phone Numbers
static string IsValidPhoneNumber(string phoneNumber)
{
// Regex to check valid phone number.
string pattern = @"^[+]{1}(?:[0-9\\-\\(\\)\\/" +
"\\.]\\s?){6,15}[0-9]{1}$";
// If the phone number is empty return false
if (string.IsNullOrEmpty(phoneNumber))
{
return "false";
}
// Return true if the phone number
// matched the Regex
if (Regex.IsMatch(phoneNumber, pattern))
{
return "true";
}
else
{
return "false";
}
}
// Driver Code
static void Main(string[] args)
{
// Test Case 1:
string str1 = "+919136812895";
Console.WriteLine(IsValidPhoneNumber(str1));
// Test Case 2:
string str2 = "+91 9136812895";
Console.WriteLine(IsValidPhoneNumber(str2));
// Test Case 3:
string str3 = "+123 123456";
Console.WriteLine(IsValidPhoneNumber(str3));
// Test Case 4:
string str4 = "654294563";
Console.WriteLine(IsValidPhoneNumber(str4));
}
}
Javascript
// Function to validate the International Phone Numbers
function isValidPhoneNumber(phoneNumber) {
// Regex to check valid phone number.
const pattern = /^[+]{1}(?:[0-9\-\\(\\)\\/.]\s?){6,15}[0-9]{1}$/;
// If the phone number is empty return false
if (!phoneNumber) {
return "false";
}
// Return true if the phone number
// matched the Regex
if (pattern.test(phoneNumber)) {
return "true";
} else {
return "false";
}
}
// Driver Code
// Test Case 1:
const str1 = "+919136812895";
console.log(isValidPhoneNumber(str1));
// Test Case 2:
const str2 = "+91 9136812895";
console.log(isValidPhoneNumber(str2));
// Test Case 3:
const str3 = "+123 123456";
console.log(isValidPhoneNumber(str3));
// Test Case 4:
const str4 = "654294563";
console.log(isValidPhoneNumber(str4));
Output
truetruetruefalse
Time Complexity: O(N) for each testcase, where N is the length of the given string.
Auxiliary Space: O(1)
Related Articles:
- How to write Regular Expressions?
- Program to find all match of a regex in a string
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