C/C++ 数据结构优先级队列的实现(使用二级指针)

#include <iostream>
#include <Windows.h>
#include <iomanip>
//优先级队列的实现
using namespace std;
#define MaxSize 5
typedef int DataType; //队列中的元素类型

typedef struct _QNode { //结点结构
    int priority; //每个节点的优先级,0 最低优先级，9 最高优先级，优先级相同，取第一个节点
    DataType data;
    struct _QNode* next;
}QNode;
typedef QNode* QueuePtr;
typedef struct Queue
{
    int length; //队列的长度
    QueuePtr front; //队头指针
    QueuePtr rear; //队尾指针
}LinkQueue;
//队列初始化，将队列初始化为空队列
void InitQueue(LinkQueue* LQ)
{
    if (!LQ) return;
    LQ->length = 0;
    LQ->front = LQ->rear = NULL; //把对头和队尾指针同时置 0
}
//判断队列为空
int IsEmpty(LinkQueue* LQ)
{
    if (!LQ) return 0;
    if (LQ->front == NULL)
    {
        return 1;
    }
    return 0;
}
//判断队列是否为满
int IsFull(LinkQueue* LQ)
{
    if (!LQ) return 0;
    if (LQ->length == MaxSize)
    {
        return 1;
    }
    return 0;
}
//入队,将元素 data 插入到队列 LQ 中
int EnterQueue(LinkQueue* LQ, DataType data, int priority) {
    if (!LQ) return 0;
    if (IsFull(LQ)) {
        cout << "无法插入元素 " << data << ", 队列已满!" << endl;
        return 0;
    }
    QNode* qNode = new QNode;
    qNode->data = data;
    qNode->priority = priority;
    qNode->next = NULL;
    if (IsEmpty(LQ)) {//空队列
        LQ->front = LQ->rear = qNode;
    }
    else {
        LQ->rear->next = qNode;//在队尾插入节点 qNode
        LQ->rear = qNode; //队尾指向新插入的节点
    }
    LQ->length++;
    return 1;
}
//出队，遍历队列，找到队列中优先级最高的元素 data 出队
int DeleteQueue(LinkQueue* LQ, DataType* data) {
    QNode** prev = NULL, * prev_node = NULL;//保存当前已选举的最高优先级节上一个节点的指针地址。
    QNode* last = NULL, * tmp = NULL; //last是已选举的最高优先级的前一个结点，tmp是已选举的最高优先级，即将要删除的结点
    if (!LQ || IsEmpty(LQ)) {
        cout << "队列为空！" << endl;
        return 0;
    }
    if (!data) return 0;
    //prev 指向队头 front 指针的地址
    prev = &(LQ->front);
    printf("第一个节点的优先级: %d\n", (*prev)->priority);
    last = LQ->front;
    tmp = last->next;
    while (tmp) {
        if (tmp->priority > (*prev)->priority) {
            printf("抓到个更大优先级的节点[priority: %d]\n",
                tmp->priority);
            prev = &(last->next);
            prev_node = last;
        }
        last = tmp;
        tmp = tmp->next;
    }
    *data = (*prev)->data;
    tmp = *prev;
    *prev = (*prev)->next;
    delete tmp;
    LQ->length--;
    //接下来存在 2 种情况需要分别对待
    //1.删除的是首节点,而且队列长度为零
    if (LQ->length == 0) {
        LQ->rear = NULL;
    }
    //2.删除的是尾部节点
    if (prev_node && prev_node->next == NULL) {
        LQ->rear = prev_node;
    }
    return 1;
}
//打印队列中的各元素
void PrintQueue(LinkQueue* LQ)
{
    QueuePtr tmp;
    if (!LQ) return;
    if (LQ->front == NULL) {
        cout << "队列为空！";
        return;
    }
    tmp = LQ->front;
    while (tmp)
    {
        cout << setw(4) << tmp->data << "[" << tmp->priority << "]";
        tmp = tmp->next;
    }
    cout << endl;
}
//获取队首元素，不出队
int GetHead(LinkQueue* LQ, DataType* data)
{
    if (!LQ || IsEmpty(LQ))
    {
        cout << "队列为空!" << endl;
        return 0;
    }
    if (!data) return 0;
    *data = LQ->front->data;
    return 1;
}
//清空队列
void ClearQueue(LinkQueue* LQ)
{
    if (!LQ) return;
    while (LQ->front) {
        QueuePtr tmp = LQ->front->next;
        delete LQ->front;
        LQ->front = tmp;
    }
    LQ->front = LQ->rear = NULL;
    LQ->length = 0;
}
//获取队列中元素的个数
int getLength(LinkQueue* LQ) {
    if (!LQ) return 0;
    return LQ->length;
}
int main()
{
    LinkQueue* LQ = new LinkQueue;
    DataType data = -1;
    //初始化队列
    InitQueue(LQ);
    //入队
    for (int i = 0; i < 5; i++) {
        EnterQueue(LQ, i + 10, i);
    }
    //打印队列中的元素
    printf("队列中的元素(总共%d 个)：", getLength(LQ));
    PrintQueue(LQ);
    cout << endl;
    //出队
    for (int i = 0; i < 5; i++) {
        if (DeleteQueue(LQ, &data)) {
            cout << "出队的元素是：" << data << endl;
        }
        else {
            cout << "出队失败！" << endl;
        }
    }
    //打印队列中的元素
    printf("出队五个元素后，队列中剩下的元素[%d]：\n", getLength(LQ));
    PrintQueue(LQ);
    cout << endl;
    ClearQueue(LQ);
    cout << "清空队列!\n";
    PrintQueue(LQ);
    //清理资源
    delete LQ;
    system("pause");
    return 0;
}