java-pattern-syntax-checker.java

//Pattern Syntax Checker Problem
/*
Using Regex, we can easily match or search for patterns in a text. Before searching for a pattern, we have to specify one using some well-defined syntax.

In this problem, you are given a pattern. You have to check whether the syntax of the given pattern is valid.

Note: In this problem, a regex is only valid if you can compile it using the Pattern.compile method.

Input Format:

The first line of input contains an integer N, denoting the number of test cases. The next N lines contain a string of any printable characters representing the pattern of a regex.

Output Format:

For each test case, print Valid if the syntax of the given pattern is correct. Otherwise, print Invalid. Do not print the quotes.

Sample Input:

3
([A-Z])(.+)
[AZ[a-z](a-z)
batcatpat(nat

Sample Output:

Valid
Invalid
Invalid


*/

import java.util.Scanner;
import java.util.regex.*;

public class Solution
{
	public static void main(String[] args){
		Scanner in = new Scanner(System.in);
		int testCases = Integer.parseInt(in.nextLine());
		while(testCases-- >0){
			String pattern = in.nextLine();
          	//Write your code
            try {
                Pattern.compile(pattern);
                System.out.println("Valid");
            } catch(PatternSyntaxException e){
                System.out.println("Invalid");
            }

		}
	}
}