HackerRank Problem Java Regex 2 – Duplicate Words Solution

1. We remove the second occurrence of bye and the second and third occurrences of world from Goodbye bye bye world world world to get Goodbye bye world.
2. We remove the second occurrence of went and the second and third occurrences of to from Sam went went to to to his business to get Sam went to his business.
3. We remove the second occurrence of is, the second occurrence of the, and the second occurrence of eyefrom Reya is is the the best player in eye eye game to get Reya is the best player in eye game.
4. The sentence in inthe has no repeated words, so we do not modify it.
5. We remove the second occurrence of ab from Hello hello Ab aB to get Hello Ab. It’s important to note that our matching is case-insensitive, and we specifically retained the first occurrence of the matched word in our final string.

DuplicateWords.java :

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class DuplicateWords {

public static void main(String[] args) {

String regex = "\\b([a-z]+)\\b(?:\\s+\\1\\b)+";
 Pattern p = Pattern.compile(regex, Pattern.CASE_INSENSITIVE);

Scanner in = new Scanner(System.in);
 int numSentences = Integer.parseInt(in.nextLine());
 
 while (numSentences-- > 0) {
 String input = in.nextLine();
 
 Matcher m = p.matcher(input);
 
 // Check for subsequences of input that match the compiled pattern
 while (m.find()) {
 input = input.replaceAll(m.group(), m.group(1));
 }
 
 // Prints the modified sentence.
 System.out.println(input);
 }

 in.close();
 }
}