队列的链式实现(C语言)

/* Queue.h */

#ifndef QUEUE_H_INCLUDED
#define QUEUE_H_INCLUDED
#include <stdio.h>
#include <stdlib.h>

struct Queue_Array {
    int element;
    struct Queue_Array* next;
};
typedef struct Queue_Array* Q_Array;

struct _Queue {
    Q_Array q;
    Q_Array Front;
    Q_Array Rear;
};

typedef struct _Queue* Queue;

/* Queue Operation */
int isEmpty(Queue Q);
void CreateQueue(Queue Q);
void make_Queue_Empty(Queue Q);
void Enqueue(int Elmt, Queue Q);
int Front(Queue Q);
void Dequeue(Queue Q);
int FrontAndDequeue(Queue Q);
void printQueue(Queue Q);

#endif // QUEUE_H_INCLUDED

/* Queue.c */

#include "Queue.h"

int isEmpty(Queue Q) {
	return (Q->Front == Q->Rear);
}

void CreateQueue(Queue Q) {

    Q_Array q   =   (Q_Array)malloc(sizeof(struct Queue_Array));
    q->element  =   0;
    q->next     =   NULL;
    Q->Front    =   Q->Rear = q;
}

void Enqueue(int Elmt, Queue Q) {

    Q_Array q       =   (Q_Array) malloc (sizeof(struct Queue_Array));
    q->element      =   Elmt;
    q->next         =   NULL;
    Q->Rear->next   =   q;
    Q->Rear         =   q;
}

int Front(Queue Q) {
    return Q->Front->element;
}

void Dequeue(Queue Q) {

    Q_Array q   = Q->Front;
    Q->Front    = Q->Front->next;
    free(q);

}

int FrontAndDequeue(Queue Q) {

    int frontElmt;
    Q_Array q   =   Q->Front;
    frontElmt   =   q->element;
    Q->Front    =   Q->Front->next;
    free(q);
    return frontElmt;
}

void make_Queue_Empty(Queue Q) {

    Q_Array q = Q->Front;

    while(q != Q->Rear) {

        Q->Front = Q->Front->next;
        free(q);
        q = Q->Front;
    }

    Q->Front = Q->Rear = NULL;
    Q->q     =   NULL;
    free(q);
}

void printQueue(Queue Q) {

    Q_Array q = Q->Front;

    while (q != Q->Rear->next) {

        printf("%d ", q->element);
        q = q->next;
    }
    printf("\n");
}

测试：

/* main.c */

#include "Queue.h"

int main()
{
    Queue Q  = (Queue) malloc (sizeof(struct _Queue));
    Q->Front = NULL;
    Q->q     = NULL;
    Q->Rear  = NULL;

    CreateQueue(Q);

    Enqueue(1, Q);
    Enqueue(3, Q);
    Enqueue(5, Q);
    Enqueue(7, Q);
    Enqueue(9, Q);
    Enqueue(11, Q);

    printQueue(Q);
    Dequeue(Q);
    printQueue(Q);

    printf("Queue's front element is %d\n", Front(Q));
    FrontAndDequeue(Q);
    printf("Queue's front element is %d\n", Front(Q));

    printQueue(Q);
    return 0;
}

结果：