232. Implement Queue using Stacks

Implement the following operations of a queue using stacks.

push(x) -- Push element x to the back of queue. pop() -- Removes the element from in front of queue. peek() -- Get the front element. empty() -- Return whether the queue is empty.

class MyQueue {
    ArrayDeque< Integer> queue = new ArrayDeque<>();
    /** Push element x to the back of queue. */
    public void push(int x) {
        queue.offer(x);
    }

    /** Removes the element from in front of queue and returns that element. */
    public int pop() {
        int e = queue.peek();
        queue.poll();
        return e;
    }

    /** Get the front element. */
    public int peek() {
        return queue.peek();
    }

    /** Returns whether the queue is empty. */
    public boolean empty() {
        return queue.isEmpty();
    }
}

/**
 * Your MyQueue object will be instantiated and called as such:
 * MyQueue obj = new MyQueue();
 * obj.push(x);
 * int param_2 = obj.pop();
 * int param_3 = obj.peek();
 * boolean param_4 = obj.empty();
 */