Program to check valid mobile number

Mobile Number validation criteria:

• The first digit should contain number between 7 to 9.
• The rest 9 digit can contain any number between 0 to 9.
• The mobile number can have 11 digits also by including 0 at the starting.
• The mobile number can be of 12 digits also by including 91 at the starting

The number which satisfies the above criteria, is a valid mobile Number. 
Examples:

Input : Enter Mobile Number:
        7873923408
Output :Valid Mobile Number

Input : Enter Mobile Number:
        5678729234
Output :Invalid Mobile Number

Prerequisites : Java Regular Expressions

C++

// C++ program to check if given mobile number
// is valid.
#include <iostream>
#include <regex>
using namespace std;

bool isValid(string s)
{
    // The given argument to pattern()
    // is regular expression. With the help of
    // regular expression we can validate mobile
    // number.
    // 1) Begins with 0 or 91
    // 2) Then contains 7 or 8 or 9.
    // 3) Then contains 9 digits
  const regex pattern("(0|91)?[7-9][0-9]{9}");

  // regex_match() is used to
  // to find match between given number
  // and regular expression
  if(regex_match(s, pattern))
  {
    return true;
  }
  else
  {
    return false;
  }
}

// Driver Code
int main()
{
  string s = "347873923408";
  if(isValid(s))
  {
      cout << "Valid";
  }
  else
  {
      cout<<"Invalid";
  }
  return 0;
}

// This code is contributed by yuvraj_chandra

Java

// Java program to check if given mobile number
// is valid.
import java.util.regex.*;
import java.util.Scanner;

class GFG{

public static boolean isValid(String s)
{

    // The given argument to compile() method
    // is regular expression. With the help of
    // regular expression we can validate mobile
    // number.
    // 1) Begins with 0 or 91
    // 2) Then contains 7 or 8 or 9.
    // 3) Then contains 9 digits
    Pattern p = Pattern.compile("(0|91)?[7-9][0-9]{9}");

    // Pattern class contains matcher() method
    // to find matching between given number
    // and regular expression
    Matcher m = p.matcher(s);
    return (m.find() && m.group().equals(s));
}

// Driver code
public static void main(String[] args)
{
    String s = "347873923408";

    if (isValid(s))
        System.out.println("Valid Number");
    else
        System.out.println("Invalid Number");
}
}

Python

# Python program to check if
# given mobile number is valid
import re

def isValid(s):

    # 1) Begins with 0 or 91
    # 2) Then contains 7 or 8 or 9.
    # 3) Then contains 9 digits
    Pattern = re.compile("(0|91)?[7-9][0-9]{9}")
    return Pattern.match(s)

# Driver Code
s = "347873923408"
if (isValid(s)):
    print ("Valid Number")
else :
    print ("Invalid Number")


# This code is contributed by rishabh_jain

Output:

Invalid Number