C语言结构及队列实现示例详解

// 链式结构：表示队列
#pragma once
#include <stdlib.h>
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
typedef int QDatatype;
typedef struct QueueNode
{
    QDatatype data;
    struct QueueNode* next;
}QNode;
typedef struct Queue
{
    QNode* phead;
    QNode* ptail;
    int size;
}Queue;
//初始化队列
void QueueInit(Queue* pq);
//队尾入队列
void QueuePush(Queue* pq , QDatatype x);
//队头出队列
void QueuePop(Queue* pq);
//获取队头元素
QDatatype QueueFront(Queue* pq);
//获取队尾元素
QDatatype QueueBack(Queue* pq);
//队列大小
int QueueSize(Queue* pq);
//判断队列是否为空
bool QueueEmpty(Queue* pq);
//销毁队列
void QueueDestory(Queue* pq);

#define _CRT_SECURE_NO_WARNINGS 1
#include "Queue.h"
//初始化队列
void QueueInit(Queue* pq)
{
    assert(pq);
    pq->phead = NULL;
    pq->ptail = NULL;
    pq->size = 0;
}
//销毁队列
void QueueDestory(Queue* pq)
{
    QNode* cur = pq->phead ;
    while (cur)
    {
        /*QNode* tmp = cur;
        cur = cur->next;
        free(tmp);*/
        QNode* next = cur->next;
        free(cur);
        cur = next;
    }
    pq->phead = pq->ptail = NULL;
    pq->size = 0;
}
//队尾入队列
void QueuePush(Queue* pq, QDatatype x)
{
    assert(pq);
    QNode* newnode = (QNode*)malloc(sizeof(QNode));
    if (newnode == NULL)
    {
        perror("malloc");
        return;
    }
    newnode->data = x;
    newnode->next = NULL;
    if (pq->phead == NULL)//isEmpty
    {
        assert(pq->ptail==NULL);
        pq->phead = newnode;
        pq->ptail = newnode;
    }
    else
    {
        pq->ptail->next = newnode;
        pq->ptail = newnode;
    }
    pq->size++;
}
//判断队列是否为空
bool QueueEmpty(Queue* pq)
{
    assert(pq);
    return pq->size == 0;
    //return pq->phead == NULL && pq->ptail == NULL;
}
//队头出队列
void QueuePop(Queue* pq)
{
    assert(pq);
    assert(!QueueEmpty(pq));//assert(pq->phead != NULL);
    //1、一个节点
    //2、多个节点
    if (pq->phead->next == NULL)//一个节点要注意ptail别弄成野指针
    {
        free(pq->phead);
        pq->phead = pq->ptail = NULL;
    }
    else
    {
        Queue* next = pq->phead->next;
        free(pq->phead);
        pq->phead = next;
    }
    pq->size--;
}
//获取队头元素
QDatatype QueueFront(Queue* pq)
{
    assert(pq);
    assert(!QueueEmpty(pq));
    return pq->phead->data;
}
//获取队尾元素
QDatatype QueueBack(Queue* pq)
{
    assert(pq);
    assert(!QueueEmpty(pq));
    return pq->ptail->data;
}
//队列大小
int QueueSize(Queue* pq)
{
    assert(pq);
    return pq->size;
}

//测试
#define _CRT_SECURE_NO_WARNINGS 1
#include "Queue.h"
void TestQueue()
{
    Queue q;
    QueueInit(&q);
    QueuePush(&q, 1);
    QueuePush(&q, 2);
    QueuePush(&q, 3);
    QueuePush(&q, 4);
    //QueuePop(&q);
    //QueuePop(&q);
    //QueuePop(&q);
    //while (!QueueEmpty(&q))
    //{
    //    printf("%d ", QueueFront(&q));
    //    
    //    QueuePop(&q);
    //}
    printf("\n"); 
    //printf("%d ", QueueFront(&q));
    //printf("%d ", QueueSize(&q));
    //QueuePop(&q);
    printf("%d ", QueueBack(&q));
    printf("%d ", QueueBack(&q));
    printf("%d ", QueueBack(&q));
    QueueDestory(&q);
}
int main()
{
    TestQueue();
    return 0;
}