Regular Expressions to Validate ISBN Code

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.

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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