implement-queue-using-stacks.md

<p>Implement the following operations of a queue using stacks.</p>

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

<p><b>Example:</b></p>

<pre>
MyQueue queue = new MyQueue();

queue.push(1);
queue.push(2);  
queue.peek();  // returns 1
queue.pop();   // returns 1
queue.empty(); // returns false</pre>

<p><b>Notes:</b></p>

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