Java Day 18: Queues and Stacks

Java Day 18: Queues and Stacks

Write the following declarations and implementations:

Two instance variables: one for your stack, and one for your queue.
A void pushCharacter(char ch) method that pushes a character onto a stack.
A void enqueueCharacter(char ch) method that enqueues a character in the queue instance variable.
A char popCharacter() method that pops and returns the character at the top of the stack instance variable.

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

public class Solution {
    private LinkedList stack;
    private LinkedList queue;

    public Solution() {
        this.stack = new LinkedList();
        this.queue = new LinkedList();
    }

    private char popCharacter() {
        return (char) this.stack.pop();
    }

    private void pushCharacter(char c) {
        this.stack.push(c);
    }

    private char dequeueCharacter() {
        return (char) this.queue.remove(0);
    }

    private void enqueueCharacter(char c) {
        this.queue.addLast(c);
    }
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        String input = scan.nextLine();
        scan.close();

        // Convert input String to an array of characters:
        char[] s = input.toCharArray();

        // Create a Solution object:
        Solution p = new Solution();

        // Enqueue/Push all chars to their respective data structures:
        for (char c : s) {
            p.pushCharacter(c);
            p.enqueueCharacter(c);
        }

        // Pop/Dequeue the chars at the head of both data structures and compare them:
        boolean isPalindrome = true;
        for (int i = 0; i < s.length/2; i++) {
            if (p.popCharacter() != p.dequeueCharacter()) {
                isPalindrome = false;                
                break;
            }
        }

        //Finally, print whether string s is palindrome or not.
        System.out.println( "The word, " + input + ", is " 
                           + ( (!isPalindrome) ? "not a palindrome." : "a palindrome." ) );
    }
}