Question

/**

* Write a recursive function that accepts a Queue<Integer>. It

* should change every int in this queue to be double its original

* value. You may NOT use loops or any other data structures besides

* the queue passed in as a parameter. You may use a helper function.

* @param q

*/

public static void doubleElements(Queue<Integer> q) {}

Answer 1

import java.util.ArrayDeque;
import java.util.Queue;

public class DoubleElements {

    /**
     * Write a recursive function that accepts a Queue<Integer>. It
     * <p>
     * should change every int in this queue to be double its original
     * <p>
     * value. You may NOT use loops or any other data structures besides
     * <p>
     * the queue passed in as a parameter. You may use a helper function.
     *
     * @param q
     */
    public static void doubleElementsHelper(Queue<Integer> q) {
        doubleElementsHelper(q, q.size());
    }

    public static void doubleElementsHelper(Queue<Integer> q, int size) {
        if (size > 0) {
            int num = q.remove();
            q.add(num*2);
            doubleElementsHelper(q, size-1);
        }
    }

    public static void main(String[] args) {
        Queue<Integer> queue = new ArrayDeque<>();
        queue.add(1);
        queue.add(2);
        queue.add(3);
        System.out.println("Original queue: " + queue);
        doubleElementsHelper(queue);
        System.out.println("Modified queue: " + queue);
    }
}