队列的链表实现

Queue.h:

#ifndef QUEUE_H
#define QUEUE_H

typedef char ElementType;

struct Node;//队列节点的结构体
typedef struct Node *PtrToNode;

struct PtrsToList;//指向队列节点的结构体
typedef struct PtrsToList *Queue;

int IsEmpty(Queue Q);
Queue CreatQueue();
void MakeEmpty(Queue Q);
void Enqueue(Queue Q, ElementType X);
void Dequeue(Queue Q);
ElementType Front(Queue Q);
ElementType FrontAndDequeue(Queue Q);
void PrintQueue(Queue Q);

#endif

LinkedQueue.c:

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

struct Node{
    ElementType Element;
    PtrToNode Next;
};

struct PtrsToList{
    PtrToNode Rear;
    PtrToNode Front;
};

int IsEmpty(Queue Q)
{
    return Q->Front == NULL;//Q->Rear == NULL;
}

Queue CreatQueue()
{
    Queue Q;
    Q = (Queue)malloc(sizeof(struct PtrsToList));
    if(Q == NULL)
        printf("Malloc failure!");
    else
    {
        Q->Rear = Q->Front = NULL;
        MakeEmpty(Q);
    }
    return Q;
}

void MakeEmpty(Queue Q)
{
    if(Q == NULL)
        printf("Please creatqueue first!");
    else
    {
        while(!IsEmpty(Q))
            Dequeue(Q);
    }
}

void DiseposeQueue(Queue Q)
{
    PtrToNode P, Tmp;
    P = Q->Front;
    while(P != NULL)
    {
        Tmp = P->Next;
        free(P);
        P = Tmp;
    }
    Q->Front = Q->Rear = NULL;
    free(Q);
}

void Enqueue(Queue Q, ElementType X)
{
    PtrToNode TmpNode;
    TmpNode = (PtrToNode)malloc(sizeof(struct Node));
    if(TmpNode == NULL)
        printf("Malloc failure!");
    else
    {
        TmpNode->Element = X;
        TmpNode->Next = NULL;
        if(IsEmpty(Q))//进队的是第一个元素
        {
            Q->Front = TmpNode;
            Q->Rear = TmpNode;
        }
        else
        {
            Q->Rear->Next = TmpNode;
            Q->Rear = TmpNode;
        }
    }
    //Q = NULL;用来测试Q其实是传来指针的副本
}

void Dequeue(Queue Q)
{
    PtrToNode FrontNode;
    if(!IsEmpty(Q))
    {
        FrontNode = Q->Front;
        if(Q->Front == Q->Rear)//只有一个元素在队中
            Q->Front = Q->Rear = NULL;
        else
            Q->Front = Q->Front->Next;
        free(FrontNode);
    }
}

ElementType Front(Queue Q)
{
    if(!IsEmpty)
        return Q->Front->Element;
    printf("Queue is empty!");
    return 0;
}

ElementType FrontAndDequeue(Queue Q)
{
    PtrToNode FrontCell;
    ElementType FrontElement;
    if(!IsEmpty(Q))
    {
        FrontCell = Q->Front;
        if(Q->Front == Q->Rear)
            Q->Front = Q->Rear = NULL;
        else
            Q->Front = Q->Front->Next;
        FrontElement = FrontCell->Element;
        free(FrontCell);
    }
    return FrontElement;
}
void PrintQueue(Queue Q)
{
    PtrToNode Pt;
    Pt = Q->Front;
    while(Pt->Next != NULL)
    {
        printf("%c-", Pt->Element);
        Pt = Pt->Next;
    }
    printf("%c\n", Pt->Element);
}