C实现队列

队列特点先进先出

队列声明

 

#ifndef _ArrayQueue_h

struct QueueRecord;
typedef struct QueueRecord *Queue;

int IsEmpty(Queue Q);
int IsFull(Queue Q);
Queue CreateQueue(int MaxElements);
void DisposeQueue(Queue Q);
void MakeEmpty(Queue Q);
void Enqueue(int X, Queue Q);
int Front(Queue Q);
void Dequeue(Queue Q);
int FrontAndDequeue(Queue Q);

#endif

队列实现

 

 

#include <stdio.h>    // stderr
#include <stdlib.h>   // NULL
#include "ArrayQueue.h"

#define MinQueueSize (5)

/* 队列的类型声明 */
struct QueueRecord
{
    int Capacity;
    int Front;
    int Rear;
    int Size;
    int *Array;
};

/* 测试队列是否为空 */
int IsEmpty(Queue Q)
{
    return Q->Size == 0;
}

/* 测试队列是否已满 */
int IsFull(Queue Q)
{
    return Q->Size == Q->Capacity;
}

/* 队列的创建 数组实现 */
Queue CreateQueue(int MaxElements)
{
    Queue Q;
    if(MaxElements < MinQueueSize)
        fprintf(stderr, "Queue size is too small");
    Q = malloc(sizeof(struct QueueRecord));
    if(Q == NULL)
        fprintf(stderr, "Out of space");
    Q->Array = malloc(sizeof(int) * MaxElements);
    if(Q->Array == NULL)
        fprintf(stderr, "Out of space");
    Q->Capacity = MaxElements;
    MakeEmpty(Q);

    return Q;
}

/* 释放队列 */
void DisposeQueue(Queue Q)
{
    if(Q != NULL)
    {
        free(Q -> Array);
        free(Q);
    }
}

/* 构造空队列 */
void MakeEmpty(Queue Q)
{
    Q->Size = 0;
    Q->Front = 1;
    Q->Rear = 0;
}

/* 入队 */
static int Succ(int Value, Queue Q)
{
    if(++Value == Q->Capacity)
        Value = 0;
    return Value;
}

void Enqueue(int X, Queue Q)
{
    if(IsFull(Q))
        fprintf(stderr, "Full queue");
    else
    {
        Q->Size++;
        Q->Rear = Succ(Q->Rear, Q);
        Q->Array[Q->Rear] = X;
    }
}

/* 将队列头返回 */
int Front(Queue Q)
{
    if(!IsEmpty(Q))
        return Q->Array[Q->Front];
    fprintf(stderr, "Empty queue");
    return 0;
}

/* 出队列 */
void Dequeue(Queue Q)
{
    if(IsEmpty(Q))
        fprintf(stderr, "Empty queue");
    else
    {
        Q->Size--;
        Q->Front = Succ(Q->Front, Q);
    }
}

/* 将队列头元素返回并出队列 */
int FrontAndDequeue(Queue Q)
{
    int tmp;
    if(!IsEmpty(Q))
    {
            tmp = Q->Array[Q->Front];
            Q->Size--;
            Q->Front = Succ(Q->Front, Q);
            return tmp;
    }
    fprintf(stderr, "Empty queue");
    return 0;
}

测试队列

 

 

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

int main(void)
{
    Queue q = CreateQueue(7);

    Enqueue(10, q);
    Enqueue(22, q);
    Enqueue(1, q);
    Enqueue(32, q);
    Enqueue(56, q);
    Enqueue(6, q);
    Enqueue(78, q);
    printf("%d\n", FrontAndDequeue(q));
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);
    printf("%d\n", Front(q));
    Dequeue(q);

    return 0;
}