leetcode-problemset/leetcode-cn/problem (English)/化栈为队(English) [implement-queue-using-stacks-lcci].html

<p>Implement a MyQueue class which implements a queue using two stacks.</p>

&nbsp;



<p><strong>Example: </strong></p>



<pre>

MyQueue queue = new MyQueue();



queue.push(1);

queue.push(2);

queue.peek();  // return 1

queue.pop();   // return 1

queue.empty(); // return false</pre>



<p>&nbsp;</p>



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



<ul>

	<li>You must use&nbsp;<i>only</i>&nbsp;standard operations of a stack -- which means only&nbsp;<code>push to top</code>,&nbsp;<code>peek/pop from top</code>,&nbsp;<code>size</code>, and&nbsp;<code>is empty</code>&nbsp;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>



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