design-circular-queue

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Algorithms

Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle, and the last position is connected back to the first position to make a circle. It is also called &quot;Ring Buffer&quot;.

One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.

Implement the <code>MyCircularQueue</code> class:

<ul>
	<li><code>MyCircularQueue(k)</code> Initializes the object with the size of the queue to be <code>k</code>.</li>
	<li><code>int Front()</code> Gets the front item from the queue. If the queue is empty, return <code>-1</code>.</li>
	<li><code>int Rear()</code> Gets the last item from the queue. If the queue is empty, return <code>-1</code>.</li>
	<li><code>boolean enQueue(int value)</code> Inserts an element into the circular queue. Return <code>true</code> if the operation is successful.</li>
	<li><code>boolean deQueue()</code> Deletes an element from the circular queue. Return <code>true</code> if the operation is successful.</li>
	<li><code>boolean isEmpty()</code> Checks whether the circular queue is empty or not.</li>
	<li><code>boolean isFull()</code> Checks whether the circular queue is full or not.</li>
</ul>

You must solve the problem without using the built-in queue data structure in your programming language.&nbsp;

&nbsp;
Example 1:

<pre>
Input
[&quot;MyCircularQueue&quot;, &quot;enQueue&quot;, &quot;enQueue&quot;, &quot;enQueue&quot;, &quot;enQueue&quot;, &quot;Rear&quot;, &quot;isFull&quot;, &quot;deQueue&quot;, &quot;enQueue&quot;, &quot;Rear&quot;]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
Output
[null, true, true, true, false, 3, true, true, true, 4]

Explanation
MyCircularQueue myCircularQueue = new MyCircularQueue(3);
myCircularQueue.enQueue(1); // return True
myCircularQueue.enQueue(2); // return True
myCircularQueue.enQueue(3); // return True
myCircularQueue.enQueue(4); // return False
myCircularQueue.Rear(); // return 3
myCircularQueue.isFull(); // return True
myCircularQueue.deQueue(); // return True
myCircularQueue.enQueue(4); // return True
myCircularQueue.Rear(); // return 4
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= k &lt;= 1000</code></li>
	<li><code>0 &lt;= value &lt;= 1000</code></li>
	<li>At most <code>3000</code> calls will be made to&nbsp;<code>enQueue</code>, <code>deQueue</code>,&nbsp;<code>Front</code>,&nbsp;<code>Rear</code>,&nbsp;<code>isEmpty</code>, and&nbsp;<code>isFull</code>.</li>
</ul>

Design Circular Queue

Design Circular Deque

design-circular-deque

设计循环双端队列

Design Front Middle Back Queue

design-front-middle-back-queue

设计前中后队列

Design

Queue

Array

Linked List

设计你的循环队列实现。 循环队列是一种线性数据结构，其操作表现基于 FIFO（先进先出）原则并且队尾被连接在队首之后以形成一个循环。它也被称为&ldquo;环形缓冲器&rdquo;。

循环队列的一个好处是我们可以利用这个队列之前用过的空间。在一个普通队列里，一旦一个队列满了，我们就不能插入下一个元素，即使在队列前面仍有空间。但是使用循环队列，我们能使用这些空间去存储新的值。

你的实现应该支持如下操作：

<ul>
	<li><code>MyCircularQueue(k)</code>: 构造器，设置队列长度为 k 。</li>
	<li><code>Front</code>: 从队首获取元素。如果队列为空，返回 -1 。</li>
	<li><code>Rear</code>: 获取队尾元素。如果队列为空，返回 -1 。</li>
	<li><code>enQueue(value)</code>: 向循环队列插入一个元素。如果成功插入则返回真。</li>
	<li><code>deQueue()</code>: 从循环队列中删除一个元素。如果成功删除则返回真。</li>
	<li><code>isEmpty()</code>: 检查循环队列是否为空。</li>
	<li><code>isFull()</code>: 检查循环队列是否已满。</li>
</ul>

&nbsp;

示例：

<pre>MyCircularQueue circularQueue = new MyCircularQueue(3); // 设置长度为 3
circularQueue.enQueue(1); &nbsp;// 返回 true
circularQueue.enQueue(2); &nbsp;// 返回 true
circularQueue.enQueue(3); &nbsp;// 返回 true
circularQueue.enQueue(4); &nbsp;// 返回 false，队列已满
circularQueue.Rear(); &nbsp;// 返回 3
circularQueue.isFull(); &nbsp;// 返回 true
circularQueue.deQueue(); &nbsp;// 返回 true
circularQueue.enQueue(4); &nbsp;// 返回 true
circularQueue.Rear(); &nbsp;// 返回 4</pre>

&nbsp;

提示：

<ul>
	<li>所有的值都在 0&nbsp;至 1000 的范围内；</li>
	<li>操作数将在 1 至 1000 的范围内；</li>
	<li>请不要使用内置的队列库。</li>
</ul>