Implement Stack using Queues

Implement the following operations of a stack using queues.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• empty() -- Return whether the stack is empty.

Notes:

• You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
• Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
• You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

Update (2015-06-11):
The class name of the Java function had been updated to MyStack instead of Stack.

class MyStack {
 
    Queue<Integer> queue1 = new LinkedList<Integer>();
    Queue<Integer> queue2 = new LinkedList<Integer>();
    int size = 0;
 
    // Push element x onto stack.
    public void push(int x) {
        queue1.add(x);
        size++;
    }

    // Removes the element on top of the stack.
    public void pop() {
        int tmp = size;
        while (tmp-- > 1) {
            queue2.add(queue1.poll());
        }
        queue1.poll();
        while (!queue2.isEmpty()) {
            queue1.add(queue2.poll());
        }
        size--;
    }

    // Get the top element.
    public int top() {
        int tmp = size;
        while (tmp-- > 1) {
            queue2.add(queue1.poll());
        }
        int top = queue1.poll();
        queue2.add(top);
        while (!queue2.isEmpty()) {
            queue1.add(queue2.poll());
        }
        return top;
    }

    // Return whether the stack is empty.
    public boolean empty() {
        return size == 0;
    }
}

====

class MyStack {
 
    Queue<Integer> queue1 = new LinkedList<Integer>();
    int size = 0;
 
    // Push element x onto stack.
    public void push(int x) {
        queue1.offer(x);
        size++;
    }

    // Removes the element on top of the stack.
    public void pop() {
        for (int i = 0; i < size - 1; i++) {
            queue1.offer(queue1.poll());
        }
        queue1.poll();
        size--;
    }

    // Get the top element.
    public int top() {
        for (int i = 0; i < size - 1; i++) {
            queue1.offer(queue1.poll());
        }
        int top = queue1.poll();
        queue1.offer(top);
        return top;
    }

    // Return whether the stack is empty.
    public boolean empty() {
        return size == 0;
    }
}

===========

class MyStack {
   
    Queue<Integer> queue1 = new LinkedList<Integer>();
   
    // Push element x onto stack.
    public void push(int x) {
        queue1.offer(x);
        int count = queue1.size();
        while (count-- > 1) {
            queue1.offer(queue1.poll());
        }
    }

    // Removes the element on top of the stack.
    public void pop() {
        queue1.poll();
    }

    // Get the top element.
    public int top() {
       return queue1.peek();
    }

    // Return whether the stack is empty.
    public boolean empty() {
        return queue1.isEmpty();
    }
}