队列的链表实现

queue.h:

#ifndef QUEUE_H_INCLUDED
#define QUEUE_H_INCLUDED
struct Node;
typedef struct Node QNode;
struct Queue;
typedef struct Queue *PtrQ;

PtrQ CreateQueue();
void MakeEmpty(PtrQ Q);
int DeQueue(PtrQ Q);
void EnQueue(int X, PtrQ Q);

#endif // QUEUE_H_INCLUDED

实现文件

implementation.c:

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

typedef struct Node{
    int Data;
    struct Node *Next;
}QNode;

typedef struct Queue{
    QNode *Rear;
    QNode *Front;
}*PtrQ;

PtrQ CreateQueue(){
    PtrQ Q;
    Q = malloc(sizeof(struct Queue));
    MakeEmpty(Q);
    return Q;
}

void MakeEmpty(PtrQ Q) {
    Q->Rear = Q->Front = NULL;
}

int DeQueue(PtrQ Q) {
    QNode *FirstCell;
    int FirstElem;
    if(Q->Front == NULL){
        printf("Error, EmptyQueue!");
        return -1;
    }
    FirstCell = Q->Front;
    if(Q->Rear == Q->Front) {
        Q->Rear = Q->Front = NULL;
    } else {
        Q->Front = Q->Front->Next;
    }
    FirstElem = FirstCell->Data;
    free(FirstCell);
    return FirstElem;
}

void EnQueue(int X, PtrQ Q) {
    QNode *TmpCell;
    TmpCell = malloc(sizeof(struct Node));
    TmpCell->Next = NULL;
    TmpCell->Data = X;
    if(Q->Front == NULL) {
        Q->Rear = TmpCell;
        Q->Front = TmpCell;
    } else if(Q->Front == Q->Rear) {
        Q->Rear = TmpCell;
        Q->Front->Next = Q->Rear;
    } else{
        Q->Rear->Next = TmpCell;
        Q->Rear = TmpCell;
    }
}

测试文件：

main.c:

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

int main()
{
    PtrQ Q;
    int a, b, c;
    Q = CreateQueue();
    EnQueue(1, Q);
    EnQueue(2, Q);
    a = DeQueue(Q);
    b = DeQueue(Q);
    printf("%d ", a);
    EnQueue(3, Q);
    c = DeQueue(Q);
    printf("%d ", b);
    printf("%d", c);
    return 0;
}