Interview Question for Software Engineer / Developers


Country: Russia
Interview Type: In-Person




Comment hidden because of low score. Click to expand.
2
of 2 vote

public class StackBy2Queues<E> {

	private Queue<E> queue1 = new LinkedList<E>();
	private Queue<E> queue2 = new LinkedList<E>();;

	public boolean empty() {

		return queue2.isEmpty() && queue1.isEmpty();
	}

	public E peek() {
		if (queue2.isEmpty())
			return queue1.peek();
		return queue2.peek();

	}

	public synchronized int size() {
		return queue2.size() + queue1.size();
	}

	public synchronized E pop() {
		if (queue2.isEmpty())
			return queue1.poll();
		return queue2.poll();
	}

	public synchronized E push(E item) {
		if (queue2.isEmpty()) {
			queue2.add(item);
			return item;
		}
		// Move all elements from queue1 to queue2 and swap
		queue2.addAll(queue1);
		Queue<E> q = queue1;
		q.clear();
		queue1 = queue2;
		queue2 = q;
		queue2.add(item);
		return item;
	}

	public static void main(String[] args) {
		StackBy2Queues<Integer> myStack = new StackBy2Queues<>();
		for (int i = 0; i < 10; i++) {
			myStack.push(i);
		}
		System.out.println("Stack items count:" + myStack.size());
		int order = 1;
		while (!myStack.empty()) {
			System.out.println("Poped [" + order + "]: " + myStack.pop());
			order++;
		}

	}

}

- artak.a.petrosyan November 20, 2015 | Flag Reply


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