A palindrome is a word or phrase that is spelled the same forward or backward. W

Question

A palindrome is a word or phrase that is spelled the same forward or backward. Words like “pop” and “noon” are palindromes. A famous example is the phrase: “A man, a plan, a canal – Panama.” Or another, “Madam, I’m Adam.” For phrases, you have to ignore punctuation, spacing, and capitalization. The palindrome problem can be solved using a queue and a stack, putting characters simultaneously into a queue and onto a stack as the word or phrase is scanned character by character. Your program must accept a word or phrase as input and then use a queue and a stack to determine whether the input is a palindrome. It should then output to the user the phrase and the results. If you choose this problem then you must use a queue and a stack data structure to solve it.

Java Programming

Explanation / Answer

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Pallindrome
{
   public static void main (String[] args) throws java.lang.Exception
   {
       // your code goes here
       Scanner input = new Scanner(System.in);
       System.out.println("Input a phrase or word.");
       String phrase = input.nextLine();
       System.out.println("You Entered : " + phrase);
      
       String phraseWithLetters = phrase.replaceAll("[\W]", "").toLowerCase();
       System.out.println("Converted phrase : " + phraseWithLetters);
      
       int len = phraseWithLetters.length();
       Stack stack = new Stack();
       Queue queue = new LinkedList();
       char temp,temp1;
       boolean flag = false;
      
       for(int i=0;i<len;i++)
       {
           stack.push(phraseWithLetters.charAt(i));
           queue.add(phraseWithLetters.charAt(i));
       }
      
       while((!stack.isEmpty()) && (!queue.isEmpty()))
       {
           temp = (char)stack.pop();
           temp1 = (char)queue.remove();
          
           if(temp!=temp1)
           {
               flag = true;
               break;
           }
       }
      
      
       if(flag)
           System.out.println(phrase + " is not a pallindrome.");
       else
           System.out.println(phrase + " is a pallindrome.");
      
   }
}

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