队列queue的C实现

头文件——————————————————————————————

#ifndef _QUEUE_H_

#define _QUEUE_H_

#include <stdlib.h>

#define Element int

struct node

{

     Element data;

     struct node *next;

};

typedef struct node *PtrToNode;

typedef struct _Queue

{

     PtrToNode head;

     PtrToNode rear;

} *Queue;

//头进尾出

int IsEmpty(Queue q);

Queue CreateQueue();

void DestroyQueue(Queue q);

void MakeEmpty(Queue q);

void Enqueue(Element x, Queue q);

Element Front(Queue q);

Element Rear(Queue q);

void Dequeue(Queue q);

#endif

源文件————————————————————————————

#include <iostream>

#include "./Queue.h"



int IsEmpty(Queue q)

{

     return q->head == q->rear && q->head == NULL;

}

Queue CreateQueue()

{

     Queue q = (Queue)malloc(sizeof(struct _Queue));

     if(NULL == q) return NULL;

     q->head = q->rear = NULL;

     return q;

}

void DestroyQueue(Queue q)

{

     MakeEmpty(q);

     free(q);

}

void MakeEmpty(Queue q)

{

     while(!IsEmpty(q))

          Dequeue(q);

}

void Enqueue(Element x, Queue q)//头进尾出

{

     if(NULL == q) return ;

     PtrToNode p = (PtrToNode)malloc(sizeof(struct node));

     if(NULL == p) return ;

     p->data = x;

     if(IsEmpty(q))

          q->rear = p;

     p->next = q->head;

     q->head = p;

}

Element Front(Queue q)

{

     return q->head->data;

}

Element Rear(Queue q)

{

     return q->rear->data;

}

void Dequeue(Queue q)//头进尾出

{

     if(NULL == q || IsEmpty(q)) return ;

     PtrToNode prev = q->head;

     while(NULL != prev && prev != q->rear && prev->next != q->rear)

          prev = prev->next;

     if(NULL == prev) return ;

     if(prev == q->rear)

     {

          q->head = q->rear = NULL;

          free(prev);

     }

     PtrToNode tmp = prev->next;

     prev->next = NULL;

     q->rear = prev;

     free(tmp);

     /*if(q->head == q->rear)

     {

          PtrToNode tmp = q->head;

          free(tmp);

          q->head = q->rear = NULL;

     }

     PtrToNode prev = q->head;

     while(NULL != prev && prev->next->data != q->rear->data)

          prev = prev->next;

     PtrToNode tmp = prev->next;

     prev->next = NULL;

     q->rear = prev;

     free(tmp);

     */

}