Tag Content Extractor

In a tag-based language like XML or HTML, contents are enclosed between a start tag and an end tag like <tag>contents</tag>. Note that the corresponding end tag starts with a /.

Given a string of text in a tag-based language, parse this text and retrieve the contents enclosed within sequences of well-organized tags meeting the following criterion:

1. The name of the start and end tags must be same. The HTML code <h1>Hello World</h2> is not valid, because the text starts with an h1 tag and ends with a non-matching h2 tag.
2. Tags can be nested, but content between nested tags is considered not valid. For example, in <h1><a>contents</a>invalid</h1>, contents is valid but invalid is not valid.
3. Tags can consist of any printable characters.

Input Format

The first line of input contains a single integer, N (the number of lines).
The N subsequent lines each contain a line of text.

Constraints

• 1 ≤ N ≤ 100
• Each line contains a maximum of  printable characters.
• The total number of characters in all test cases will not exceed 10⁶.

Output Format

For each line, print the content enclosed within valid tags.
If a line contains multiple instances of valid content, print out each instance of valid content on a new line; if no valid content is found, print None.

Sample Input

4
<h1>Nayeem loves counseling</h1>
<h1><h1>Sanjay has no watch</h1></h1><par>So wait for a while</par>
<Amee>safat codes like a ninja</amee>
<SA premium>Imtiaz has a secret crush</SA premium>

Sample Output

Nayeem loves counseling
Sanjay has no watch
So wait for a while
None
Imtiaz has a secret crush

Solution Implementation

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class TagContentExtractor{
   
   public static void main(String[] args){
       
       Scanner in = new Scanner(System.in);
       int testCases = Integer.parseInt(in.nextLine());
       String regexPatern = "(<[^>]*>)";
       Pattern stringPatern  = Pattern.compile(regexPatern);
          while(testCases>0){
              String line = in.nextLine();
              int pos = 0;
              Matcher m = stringPatern.matcher(line);
              String previousHTMLTag = null;
              int previousTagPos = -1;
              boolean didFind = false;
              while(m.find())
              {    
                  String htmlTag = line.substring(m.start(),m.end());
                  if(htmlTag.charAt(1) != '/')
                  {
                    previousHTMLTag = htmlTag;
                       previousTagPos = m.end();
                  }else if(htmlTag.charAt(1) == '/' && previousHTMLTag != null){
                      if(previousHTMLTag.substring(1).equals(htmlTag.substring(2))&&previousHTMLTag.length()>2 && m.start()>previousTagPos+1){
                        System.out.println(line.substring(previousTagPos,m.start()));
                          didFind = true;
                      }
                    previousHTMLTag = null;
                  }
                  
              }
              System.out.print(didFind?"":"None\n");
              testCases--;
        }
          
    }
}