队列的基本操作

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队列特性:先进先出(FIFO)——先进队列的元素先出队列。来源于我们生活中的队列(先排队的先办完事)。

队列有下面几个操作:

  • InitQueue()   初始化队列
  • EnQueue()        进队列
  • DeQueue()        出队列
  • QueLength( )        队列元素个数 
  • DestroyQueue( )    销毁队列

队列可以由数组和链表两种形式实现队列操作;

下边是队两种实现的基本操作:

#include "stdafx.h"#include<iostream>using namespace std;#define OK 1#define ERROR 0#define TRUE 1#define FALSE 0#define OVERFLOW -2#define INFEASIALE -1typedef int status;typedef int QElemType;//链队列,需要带头节点struct LQnode{QElemType data;struct LQnode *next;};typedef struct{LQnode *front;LQnode *rear;}LinkQueue;status InitQueue(LinkQueue &q){LQnode *s = new LQnode;s->next = NULL;q.front = q.rear = s;    return OK;}status GetFront(LinkQueue q, QElemType &e){if (q.front == q.rear){return ERROR;}e = q.front->next->data;return OK;}status DestroyQueue(LinkQueue &q){while (q.front){q.rear = q.front->next;delete q.front;q.front = q.rear;}return OK;}status EnQueue(LinkQueue &q, QElemType x){LQnode *s = new LQnode;s->data = x;s->next = NULL;q.rear->next = s;q.rear = s;return OK;}status DeQueue(LinkQueue &q, QElemType &e){if (q.front == q.rear){return ERROR;}e = q.front->next->data;LQnode *s = q.front->next;q.front->next = q.front->next->next;if (q.rear == s)//这里是因为若队列只有一个元素时,出队一个元素后,尾指针应该指向q.front,{              //若不修改,则会变成悬垂指针q.rear = q.front;}delete s;return OK;}//循环队列,判断队列空和队列满时都有front == rear,需要区分队列空和队列满的状态//方法1:另设一个标志位以区别“空”和“满”//方法2:少用一个元素空间,约定以队列头指针在队列尾指针的下一位置(环状)上作为队列满状态//下面用第二种方法#define MAXQSIZE 10typedef struct{QElemType *base;int front;int rear;}SqQueue;status Initqueue(SqQueue &q){q.base = new QElemType[MAXQSIZE];if (!q.base){ exit(OVERFLOW);}q.front = q.rear = 0;return OK;}int QueLength(SqQueue q){return (q.rear - q.front + MAXQSIZE) % MAXQSIZE;}status EnQueue(SqQueue &q, QElemType x){if ((q.rear + 1) % MAXQSIZE == q.front){return ERROR;}q.base[q.rear] = x;q.rear = (q.rear + 1) % MAXQSIZE;return OK;}status DeQueue(SqQueue &q, QElemType &e){if (q.front == q.rear){return ERROR;}e = q.base[q.front];q.front = (q.front + 1) % MAXQSIZE;return OK;}int _tmain(int argc, _TCHAR* argv[]){LinkQueue q;InitQueue(q);SqQueue s;Initqueue(s);for (int i = 0; i < 10; i++){EnQueue(q, i);EnQueue(s, i+1);}int e;GetFront(q, e);cout << "链队的头元素为:" << endl;cout << e << endl;;cout << "链队全部出队为:" << endl;for (int j = 0; j < 10; j++){DeQueue(q, e);cout << e << ' ';}cout << endl;cout << "循环队列现在长度为:" << endl;int count = QueLength(s);cout << count << endl;cout << "循环队列全部出队为:" << endl;for (int k = 0; k < count; k++){DeQueue(s, e);cout << e << ' ';}system("pause");return 0;}

队列的一个使用例子为:离散时间模拟(比如银行业务处理)!

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