队列实现例子

 1 #ifndef QUEUE_H_
 2 #define QUEUE_H_
 3 
 4 #include <stdbool.h>
 5 #define QUEUEMAX 10
 6 
 7 typedef int Item;
 8 
 9 typedef struct node
10 {
11     Item item;
12     struct node * next;
13 } Node;
14 
15 typedef struct queue 
16 {
17     Node * front;
18     Node * rear;
19     int length;
20 } Queue;
21 
22 void InitializeQueue(Queue * pq);
23 
24 bool QueueIsEmpty(const Queue * pq);
25 
26 bool QueueIsFull(const Queue * pq);
27 
28 int QueueItemCount(const Queue * pq);
29 
30 bool EnQueue(Item item, Queue * pq);
31 
32 bool DeQueue(Item * pitem, Queue * pq);
33 
34 void ShowQueue(const Queue * pq);
35 
36 void EmptyTheQueue(Queue * pq);
37 #endif

#include <stdio.h>
#include "queue.h"

void eatline(void);

int main(void)
{
    Queue line;   
    Item temp;

    InitializeQueue(&line);

    printf("<a. add    d. delete    s. show    q. quit>\n");
    char ch;
    while(‘q‘ != (ch = getchar()))
    {
        eatline();
        if(‘a‘ != ch && ‘d‘ != ch && ‘s‘ != ch)
        {
            printf("invalid input!\n");
            printf("<a. add    d. delete    s. show    q. quit>\n");
            continue;
        }
        if(‘a‘ == ch)
        {
            if(QueueIsFull(&line))
                printf("Queue is full!\n");
            else
            {
                printf("Integer to add: ");
                scanf("%d", &temp);
                eatline();

                int result = EnQueue(temp, &line);
                printf("Putting %d into queue <%s>\n", temp, (true == result? "success" : "failed"));
            }
        }
        else if(‘d‘ == ch)
        {
            if(QueueIsEmpty(&line))
                printf("No data to delete!\n");
            else
            {
                int result = DeQueue(&temp, &line);
                printf("Remove %d from queue <%s>\n", temp, (true == result ? "success" : "failed"));
            }
        }
        else if(‘s‘ == ch)
        {
            if(QueueIsEmpty(&line))
                printf("No data to show!\n");
            else
            {
                printf("Here is the queue content:\n");
                ShowQueue(&line);
            }
        }
        printf("<a. add    d. delete    s. show    q. quit>\n");
    }
    EmptyTheQueue(&line);
    printf("Bye!\n");

    return 0;
}

void eatline(void)
{
    while(‘\n‘ != getchar())
        continue;
}

#include <stdio.h>
#include <stdlib.h>
#include "queue.h"

static void CopyToNode(Item item, Node * pn);

static void CopyToItem(Item * pitem, Node * pn);

void InitializeQueue(Queue * pq)
{
    pq->front = pq->rear = NULL;
    pq->length = 0;
}

bool QueueIsEmpty(const Queue * pq)
{
    return pq->length == 0;
}

bool QueueIsFull(const Queue * pq)
{
    return pq->length == QUEUEMAX;
}

int QueueItemCount(const Queue * pq)
{
    return pq->length;
}

bool EnQueue(Item item, Queue * pq)
{
    if(QueueIsFull(pq))
        return false;
    Node * pn = (Node *)malloc(sizeof(Node));
    if(NULL == pn)
    {
        printf("Unable to allocate memory!\n");
        exit(1);
    }
    CopyToNode(item, pn);
    pn->next = NULL;

    if(QueueIsEmpty(pq))
        pq->front = pn;
    else
        pq->rear->next = pn;
    pq->rear = pn;

    pq->length++;

    return true;
}

bool DeQueue(Item * pitem, Queue * pq)
{
    if(QueueIsEmpty(pq))
        return false;
    Node * pn;
    pn = pq->front;
    CopyToItem(pitem, pn);
    pq->front = pq->front->next;
    free(pn);
    pq->length--;

    if(0 == pq->length)
        pq->rear = NULL;

    return true;
}

void ShowQueue(const Queue * pq)
{
    Node * pn = pq->front;
    printf("[");
    while(NULL != pn)
    {
        printf("%d  ", pn->item);
        pn = pn->next;
    }
    printf("]\n");
}

void EmptyTheQueue(Queue * pq)
{
    Item dummy;
    while(!QueueIsEmpty(pq))
        DeQueue(&dummy, pq);
}

static void CopyToNode(Item item, Node * pn)
{
    pn->item = item;
}

static void CopyToItem(Item * pitem, Node * pn)
{
     *pitem = pn->item;
}