Hackerrank Java Regex 2 - Duplicate Words Solution
In this challenge, we use regular expressions (RegEx) to remove instances of words that are repeated more than once, but retain the first occurrence of any case-insensitive repeated word. For example, the words love
and to
are repeated in the sentence I love Love to To tO code
. Can you complete the code in the editor so it will turn I love Love to To tO code
into I love to code
?
To solve this challenge, complete the following three lines:
- Write a RegEx that will match any repeated word.
- Complete the second compile argument so that the compiled RegEx is case-insensitive.
- Write the two necessary arguments for replaceAll such that each repeated word is replaced with the very first instance the word found in the sentence. It must be the exact first occurrence of the word, as the expected output is case-sensitive.
Note: This challenge uses a custom checker; you will fail the challenge if you modify anything other than the three locations that the comments direct you to complete. To restore the editor's original stub code, create a new buffer by clicking on the branch icon in the top left of the editor.
Input Format
The following input is handled for you the given stub code:
The first line contains an integer, , denoting the number of sentences.
Each of the subsequent lines contains a single sentence consisting of English alphabetic letters and whitespace characters.
Constraints
- Each sentence consists of at most English alphabetic letters and whitespaces.
Output Format
Stub code in the editor prints the sentence modified by the replaceAll line to stdout. The modified string must be a modified version of the initial sentence where all repeat occurrences of each word are removed.
Sample Input
5
Goodbye bye bye world world world
Sam went went to to to his business
Reya is is the the best player in eye eye game
in inthe
Hello hello Ab aB
Sample Output
Goodbye bye world
Sam went to his business
Reya is the best player in eye game
in inthe
Hello Ab
Explanation
- We remove the second occurrence of
bye
and the second and third occurrences ofworld
fromGoodbye bye bye world world world
to getGoodbye bye world
. - We remove the second occurrence of
went
and the second and third occurrences ofto
fromSam went went to to to his business
to getSam went to his business
. - We remove the second occurrence of
is
, the second occurrence ofthe
, and the second occurrence ofeye
fromReya is is the the best player in eye eye game
to getReya is the best player in eye game
. - The sentence
in inthe
has no repeated words, so we do not modify it. - We remove the second occurrence of
ab
fromHello hello Ab aB
to getHello 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.
Solution in java8
Approach 1.
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(\\w+)(\\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(0),m.group(1));
}
// Prints the modified sentence.
System.out.println(input);
}
in.close();
}
}
Approach 2.
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(\\w+)(\\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();
}
}
Approach 3.
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(\\w+)(?:\\W+\\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();
}
}