WAP to Remove Consecutive Duplicate Characters from String

This Java program aims to remove consecutive duplicate characters from a given string. It utilizes a stack data structure to achieve this.

Remove Consecutive Duplicate Characters from String

package com.softwaretestingo.interviewprograms;
import java.util.Stack;
public class InterviewPrograms39 
{
	/*
	 * Input string : weelccoommee hhoommeee 
	 * Output string : welcome home
	 */
	public static void main(String[] args) 
	{
		String s = "weelccoommee hhoommeee";
		Stack<Character> st = new Stack<>();
		st.push(s.charAt(0));
		for (int i = 1; i<s.length(); i++ ) 
		{
			if (s.charAt(i-1) != s.charAt(i))
				st.push(s.charAt(i));
		}
		for ( Character c : st )
			System.out.print(c) ;
	}
}

Output

welcome home

Here’s a breakdown of the program:

1. Define the main method:
   • The entry point of the program is the main method.
2. Initialize the input string and create a stack:
   • The string s is initialized with the value “weelccoommee hhoommeee”.
   • A stack of characters named st is created.
3. Process the string and remove consecutive duplicates:
   • The program iterates through each character of the string using a for loop, starting from the second character.
   • It compares the current character with the previous character using the condition s.charAt(i-1) != s.charAt(i).
   • If the current character is different from the previous character, it is pushed onto the stack using st.push(s.charAt(i)).
4. Print the non-duplicate characters:
   • The program then uses an enhanced for loop to iterate over the characters in the stack.
   • Each character is printed using System.out.print(c).

The program outputs the non-duplicate characters from the original string. In this case, the output will be “welcome home”, where consecutive duplicate characters have been removed.

Alternative 1:

This Java program aims to remove consecutive duplicate characters from a given input string using regular expressions.

package com.softwaretestingo.interviewprograms;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class InterviewPrograms39_1 
{
	/*
	 * Input string : weelccoommee hhoommeee 
	 * Output string : welcome home
	 */
	public static void main(String[] args) 
	{
		String s = " weelccoomme hhommeee " ;
		Pattern pattern = Pattern.compile("(.)\\1*");
		Matcher m= pattern.matcher ( s ) ;
		String output = "";
		while ( m.find())
		{
			output= output + m.group().charAt(0);
		}
		System.out.println ( output ) ;
	}
}

Output

welcome home

Here’s a breakdown of the program:

1. Define the main method:
   • The entry point of the program is the main method.
2. Initialize the input string and compile the regex pattern:
   • The string s is initialized with the value ” weelccoomme hhommeee “.
   • A regex pattern is created using Pattern.compile(“(.)\\1*”). This pattern looks for consecutive repeated characters.
3. Create a Matcher object and find matches:
   • A Matcher object named m is created by applying the pattern on the input string s.
   • The m.find() method is used to find occurrences of the pattern in the input string.
4. Build the output string:
   • While the m.find() method continues to find matches, the program extracts the matched group using m.group().
   • The first character of each matched group is extracted using charAt(0) and added to the output string.
5. Print the output:
   • The program prints the final output string, which contains the non-duplicate characters from the original string.

The program outputs “welcome home”, where consecutive duplicate characters have been removed using regular expressions.