Question

Using a queue and a stack, implement a method that tests whether a sequence of numbers is a palindrome, that is, equal to the sequence in reverse. For example, [1,2,3,2,1] is a palindrome, but [1,2,2,3,1] is not.

Complete the following file:

QueueStackUtil.java

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class QueueStackUtil
{
public static boolean isPalindrome(int[] values)
{
Queue<Integer> queue = new LinkedList<Integer>();
Stack<Integer> stack = new Stack<Integer>();
for (int s : values)
{
// insert s into the queue and stack
}
while (queue.size() > 0)
{
// remove an element from the queue

// remove an element from the stack

// compare the removed elements

}
return ...;
}
}

Answer 1

QueueStackUtil.java

import java.util.LinkedList;
import java.util.Queue;
import java.util.Stack;

public class QueueStackUtil {
    public static boolean isPalindrome(int[] values) {
        Queue < Integer > queue = new LinkedList < Integer > ();
        Stack < Integer > stack = new Stack < Integer > ();
        for (int s: values) {
            stack.push(s);
                        queue.add(s);
        }
                int x, y;
        while (queue.size() > 0) {
            // remove an element from the queue
                        x = queue.remove();

            // remove an element from the stack
                        y = stack.pop();
                        
            // compare the removed elements
                        if(x != y)
                                break;

        }
                boolean isP;
                
                if(x != y)
                        isP = false;
                else
                        isP = true
        return isP;
    }
}

if you have any doubt, feel free to ask in the comments.