【数据结构】链队列

谨以此文记录链队列的实现：

#include 

using namespace std;

typedef int QElemType;

typedef struct QNode
{
    QElemType data;
    QNode *next;
} QNode, *QueuePtr;

typedef struct
{
    QueuePtr front = nullptr, rear = nullptr;
} LinkQueue;

void printUI()
{
    cout << "*******************************************************" << endl;
    cout << "*********  1.初始化队列                       *********" << endl;
    cout << "*********  2.销毁队列                         *********" << endl;
    cout << "*********  3.清空队列                         *********" << endl;
    cout << "*********  4.判断队列是否为空                 *********" << endl;
    cout << "*********  5.返回队列中元素个数               *********" << endl;
    cout << "*********  6.返回队列队头元素                 *********" << endl;
    cout << "*********  7.插入新的队尾元素                 *********" << endl;
    cout << "*********  8.删除队头元素                     *********" << endl;
    cout << "*********  9.初始化并创建队列                 *********" << endl;
    cout << "*********  10.输出队列元素                    *********" << endl;
    cout << "*********  11.退出                            *********" << endl;
    cout << "*******************************************************" << endl;
}


bool InitQueue(LinkQueue &Q)
{
    Q.front = Q.rear = new QNode;
    Q.front->next = nullptr;
    return true;
}


bool DestroyQueue(LinkQueue &Q)
{
    while (Q.front)
    {
        Q.rear = Q.front->next;
        delete Q.front;
        Q.front = Q.rear;
    }
    return true;
}


bool QueueEmpty(LinkQueue Q)
{
    return Q.front == Q.rear;
}


bool GetHead(LinkQueue Q, QElemType &e)
{
    if (Q.front == Q.rear)
        return false;
    e = Q.front->next->data;
    return true;
}


bool EnQueue(LinkQueue &Q, QElemType e)
{
    QNode *p = new QNode;
    p->data = e;
    p->next = nullptr;
    Q.rear->next = p;
    Q.rear = p;
    return true;
}


bool DeQueue(LinkQueue &Q, QElemType &e)
{
    if (Q.front == Q.rear)
        return false;
    QNode *p = Q.front->next;
    e = p->data;
    Q.front->next = p->next;
    if (Q.rear == p)
        Q.rear = Q.front;
    delete p;
    return true;
}


bool ClearQueue(LinkQueue &Q)
{
    while (Q.front != Q.rear)
    {
        QueuePtr p = Q.front->next;
        Q.front->next = p->next;
        if (Q.rear == p)
            Q.rear = Q.front;
        delete p;
    }
    return true;
}


int QueueLength(LinkQueue Q)
{
    int i = 0;
    QueuePtr p = Q.front;
    while (p->next)
    {
        i++;
        p = p->next;
    }
    return i;
}


void PrintElem(LinkQueue Q)
{
    QueuePtr p = Q.front;
    while (p->next)
    {
        cout << p->next->data << " ";
        p = p->next;
    }
    cout << endl;
}

int main()
{
    int mode;
    QElemType e;
    LinkQueue Q;
    printUI();
    while (1)
    {
        cout << "请输入选择：";
        cin >> mode;
        if (mode == 11)
            break;
        if (mode < 1 || mode > 11)
            continue;
        if ((!Q.front || !Q.rear) && mode != 1 && mode != 9)
        {
            cout << "尚未初始化" << endl;
            continue;
        }
        switch (mode)
        {
        case 1:
            if (InitQueue(Q))
                cout << "初始化成功" << endl;
            break;
        case 2:
            if (DestroyQueue(Q))
                cout << "销毁成功" << endl;
            break;
        case 3:
            if (ClearQueue(Q))
                cout << "清空成功" << endl;
            break;
        case 4:
            if (QueueEmpty(Q))
                cout << "队列为空" << endl;
            else
                cout << "队列不为空" << endl;
            break;
        case 5:
            cout << "队列元素个数为" << QueueLength(Q) << endl;
            break;
        case 6:
            if (GetHead(Q, e))
                cout << "队列头节点为" << e << endl;
            else
                cout << "获取头节点失败" << endl;
            break;
        case 7:
            cout << "请输入您要插入的元素：";
            cin >> e;
            if (EnQueue(Q, e))
                cout << "插入成功" << endl;
            else
                cout << "插入失败" << endl;
            break;
        case 8:
            if (DeQueue(Q, e))
                cout << "队头元素" << e << "已出队" << endl;
            else
                cout << "出队失败" << endl;
            break;
        case 9:
            int n;
            InitQueue(Q);
            cout << "请输入队列元素个数：";
            cin >> n;
            cout << "请输入元素：";
            while (n--)
            {
                cin >> e;
                EnQueue(Q, e);
            }
            cout << "初始化创建成功" << endl;
            break;
        case 10:
            PrintElem(Q);
            break;
        }
    }
    return 0;
}