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Regular Expressions to Validate ISBN Code

Last Updated : 23 Jul, 2025
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Given some ISBN Codes, the task is to check if they are valid or not using regular expressions. Rules for the valid codes are:

  • It is a unique 10 or 13-digit.
  • It may or may not contain a hyphen.
  • It should not contain whitespaces and other special characters.
  • It does not allow alphabet letters.

Examples:

Input: str = ”978-1-45678-123-4?
Output: True

Input: str = ”ISBN446877428FCI?
Output: False
Explanation: It should contain digits and hyphens only.

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

Create a regex pattern to validate the number as written below:   
regex = "^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-9]*[0-9]){3})?$)[\\d-]+$"

Where,

  • ^: Represents the beginning of the string.
  • ?: Either it contains or not.
  • $: Ending of the string.
  • *: Match preceding expression zero or more times
  • {n}: Match preceding expression exactly n times

Follow the below steps to implement the idea:

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

Below is the implementation of the above approach.

Java 
// Java program to validate the
// ISBN Code using Regular Expression
import java.util.regex.*;

class GFG {

    // Function to validate the
    // ISBN Code
    public static boolean isValidISBNCode(String str)
    {

        // Regex to check valid ISBN Code
        String regex
            = "^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-9]*[0-9]){3})?$)[\\d-]+$";

        // 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 regular expression.
        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 = "978-1-45678-123-4";
        System.out.println(isValidISBNCode(str1));

        // Test Case 2:
        String str2 = "1-56619-909-3";
        System.out.println(isValidISBNCode(str2));

        // Test Case 3:
        String str3 = "1207199818865";
        System.out.println(isValidISBNCode(str3));

        // Test Case 4:
        String str4 = "978-1-12345-909-4 2";
        System.out.println(isValidISBNCode(str4));

        // Test Case 5:
        String str5 = "ISBN446877428FCI";
        System.out.println(isValidISBNCode(str5));
    }
}
C++ 
// C++ program to validate the
// ISBN Code using Regular
// Expression
#include <iostream>
#include <regex>
using namespace std;

// Function to validate the
// ISBN Code
bool isValidISBNCode(string str)
{

    // Regex to check valid
    // ISBN Code.
    const regex pattern("^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-"
                        "9]*[0-9]){3})?$)[\\d-]+$");

    // 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 = "978-1-45678-123-4";
    cout << isValidISBNCode(str1) << endl;

    // Test Case 2:
    string str2 = "1-56619-909-3";
    cout << isValidISBNCode(str2) << endl;

    // Test Case 3:
    string str3 = "1207199818865";
    cout << isValidISBNCode(str3) << endl;

    // Test Case 4:
    string str4 = "978-1-12345-909-4 2";
    cout << isValidISBNCode(str4) << endl;

    // Test Case 5:
    string str5 = "ISBN446877428FCI";
    cout << isValidISBNCode(str5) << endl;

    return 0;
}
Python3 
# Python3 program to validate
# ISBN Code using Regular Expression
import re

# Function to validate
# ISBN Code


def isValidISBNCode(str):

    # Regex to check valid ISBN Code
    regex = "^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-9]*[0-9]){3})?$)[\\d-]+$"

    # 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


# Test Case 1:
str1 = "978-1-45678-123-4"
print(isValidISBNCode(str1))

# Test Case 2:
str2 = "1-56619-909-3"
print(isValidISBNCode(str2))

# Test Case 3:
str3 = "1207199818865"
print(isValidISBNCode(str3))

# Test Case 4:
str4 = "978-1-12345-909-4 2"
print(isValidISBNCode(str4))

# Test Case 5:
str5 = "ISBN446877428FCI"
print(isValidISBNCode(str5))
C# 
// C# program to validate the
// ISBN Code
// using Regular Expressions
using System;
using System.Text.RegularExpressions;
class GFG {

    // Main Method
    static void Main(string[] args)
    {

        // Input strings to Match
        // ISBN Code
        string[] str
            = { "978-1-45678-123-4", "1-56619-909-3",
                "1207199818865", "978-1-12345-909-4 2",
                "ISBN446877428FCI" };
        foreach(string s in str)
        {
            Console.WriteLine(isValidISBNCode(s) ? "true"
                                                 : "false");
        }
        Console.ReadKey();
    }

    // method containing the regex
    public static bool isValidISBNCode(string str)
    {
        string strRegex
            = @"^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-9]*[0-9]){3})?$)[\d-]+$";
        Regex re = new Regex(strRegex);
        if (re.IsMatch(str))
            return (true);
        else
            return (false);
    }
}
JavaScript 
// Javascript program to validate
// ISBN Code using Regular Expression

// Function to validate the
// ISBN Code
function isValidISBNCode(str) {
    // Regex to check valid
    // ISBN CODE
    let regex = new RegExp(/^(?=(?:[^0-9]*[0-9]){10}(?:(?:[^0-9]*[0-9]){3})?$)[\d-]+$/);

    // 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 = "978-1-45678-123-4";
console.log(isValidISBNCode(str1));

// Test Case 2:
let str2 = "1-56619-909-3";
console.log(isValidISBNCode(str2));

// Test Case 3:
let str3 = "1207199818865";
console.log(isValidISBNCode(str3));

// Test Case 4:
let str4 = "978-1-12345-909-4 2";
console.log(isValidISBNCode(str4));

// Test Case 5:
let str5 = "ISBN446877428FCI";
console.log(isValidISBNCode(str5));

Output
true
true
true
false
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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