队列（FIFO）—循环队列队列的链式存储

Posted 2021-02-16 zpchya

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1 队列的定义

队列是只允许在一端（队尾）进行插入操作，而在另一端（队头）进行删除操作的线性表。

2 队列的特点

1）先进先出是队列最大的特点，是应用中非常常见的模型，例如排队；

2）队列也属于线性表，线性表的特性队列都拥有。

3 循环队列的实现及关键点

3.1 关键点

1）队列为空的条件：队头指针等于队尾指针，即head == tial；

2）队列中保留一个元素空间，当队列满时，尾指针和头指针之间还剩一个元素空间。队列为满的条件：(tial + 1) % quenceSize == head；

3）队列中元素个数为：(tial + quenceSize - head) % quenceSize。

3.2 实现

 1 #ifndef CYCLESQUENCE_H
 2 #define CYCLESQUENCE_H
 3 
 4 typedef int ElemType;
 5 
 6 class CycleQuence {
 7 private:
 8     ElemType* m_pData;    //数组地址
 9     int m_nHead;    //首元素位置
10     int m_nTial;    //尾元素位置
11     int m_nMaxSize;    //数组长度
12 
13 public:
14     CycleQuence(int maxSize);
15     ~CycleQuence();
16     void ClearQuence() { m_nHead = 0, m_nTial = 0; }    //清空队列
17     bool EnterQuence(ElemType elem);    //入队
18     bool DeleteQuence(ElemType* pElem);    //出队
19     void VisitQuence() const;    //查看队列元素
20     bool IsEmpty() const { return m_nHead == m_nTial; }    //判断是否为空
21     bool IsFull() const { return m_nHead == (m_nTial + 1) % m_nMaxSize; }    //判断是否为满
22 };
23 
24 #endif

 1 #include "pch.h"
 2 #include "CycleSquence.h"
 3 #include <iostream>
 4 
 5 CycleQuence::CycleQuence(int maxSize)
 6 {
 7     m_nHead = 0;
 8     m_nTial = 0;
 9     m_nMaxSize = maxSize;
10     m_pData = new ElemType[maxSize];
11 }
12 
13 CycleQuence::~CycleQuence()
14 {
15     delete[] m_pData;
16 }
17 
18 bool CycleQuence::EnterQuence(ElemType elem)    //入队
19 {
20     if (IsFull())    //队满
21     {
22         std::cout << "The quence is full." << std::endl;
23         return false;
24     }
25         
26     m_pData[m_nTial] = elem;
27     m_nTial = (m_nTial + 1) % m_nMaxSize;
28     VisitQuence();
29 
30     return true;
31 }
32 
33 bool CycleQuence::DeleteQuence(ElemType* pElem)    //出队
34 {
35     if (IsEmpty())    //队空
36         return false;
37 
38     *pElem = m_pData[m_nHead];
39     m_nHead = (m_nHead + 1) % m_nMaxSize;
40     VisitQuence();
41 
42     return true;
43 }
44 
45 void CycleQuence::VisitQuence() const    //查看队列元素
46 {
47     std::cout << "The element of quence: ";
48     for (int i = m_nHead, j = 0; j < (m_nTial + m_nMaxSize - m_nHead) % m_nMaxSize; i = (i + 1) % m_nMaxSize, ++j)
49         std::cout << m_pData[i] << ‘ ‘;
50     std::cout << std::endl;
51 }

测试代码（Visual Studio 2017上测试）：

 1 #include "pch.h"
 2 #include "CycleSquence.h"
 3 #include <iostream>
 4 
 5 int main()
 6 {
 7     CycleQuence quence(5);
 8     quence.EnterQuence(1);
 9     quence.EnterQuence(2);
10     quence.EnterQuence(3);
11     quence.EnterQuence(4);
12     ElemType elem;
13     quence.DeleteQuence(&elem);
14     quence.DeleteQuence(&elem);
15     quence.DeleteQuence(&elem);
16     quence.EnterQuence(5);
17     quence.EnterQuence(6);
18     quence.EnterQuence(7);
19     quence.EnterQuence(8);
20 
21     return 0;
22 }