数据结构--循环队列
实现队列的方法很多,比如动态数组、链表,今天主要介绍循环队列
首先说用静态数组实现简单队列。
很显然,当队列满后,即便全部元素都出队,队列还是满的状态。这种情况就叫做“假溢出”,即数组中明明有可用空间,但却无法使用。
这是由定长数组的特性决定的。但我们可用改变一下思路,当队尾指针指向数组最后一个位置时,如果再有数据入队,并且队头指针没有指向数组的第一个元素,那么就让队为指针绕回到数组头部。这样就形成了一个逻辑上的环。
这样,只要队列中实际的元素数量小于数组长度减一,就可以继续入队了。
其实这是一个非常简单的数据结构,难点就是判断队空、对满,以及计算队列长度。
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const int MAX_QUEUE_SIZE = 5;
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template<typename T>
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class cyc_queue
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{
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public:
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cyc_queue()
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:m_nHead(0),
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m_nTail(0)
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{}
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//如对操作, 将数据追加到队列头部,并改变队首指针,如队成功,则返回true
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bool in_queue(const T & data)
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{
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if(full())
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//队列满
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{
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return false;
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}
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m_array[m_nTail] = data;
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m_nTail = (m_nTail + 1) % MAX_QUEUE_SIZE;
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}
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//出队操作,将队首数据复制并返回,改变队首指针
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T out_queue()
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{
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if(empty())
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{
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throw("队列已空");
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}
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T temp = m_array[m_nHead];
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m_nHead = (m_nHead + 1) % MAX_QUEUE_SIZE;
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return temp;
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}
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bool empty()
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{
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return m_nTail == m_nHead;
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}
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bool full()
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{
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return (m_nTail + 1) % MAX_QUEUE_SIZE == m_nHead;
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}
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size_t size()
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{
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return (m_nTail - m_nHead + MAX_QUEUE_SIZE) % MAX_QUEUE_SIZE;
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}
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private:
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T m_array[MAX_QUEUE_SIZE];
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int m_nHead;
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int m_nTail;
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};
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