队列（链表实现）

版权声明： https://blog.csdn.net/moon_sky1999/article/details/83998915

外接线性表（链表实现）

#pragma once

#include "chain.h"

template<class T>
class queue {
public:
    virtual ~queue() {}

    virtual bool empty() const = 0;

    virtual int size() const = 0;

    virtual T &front() = 0;

    virtual T &back() = 0;

    virtual void pop() = 0;

    virtual void push(const T &theElement) = 0;
};

template<class T>
class LinkedQueue : public queue<T> {
public:
    LinkedQueue();

    ~LinkedQueue();

    bool empty() const { return queueSize == 0; }

    int size() const { return queueSize; }

    T &front();

    T &back();

    void push(const T &theElement);

    void pop();

private:
    chainNode<T> *queueFront;
    chainNode<T> *queueBack;
    int queueSize;
};

template<class T>
LinkedQueue<T>::LinkedQueue() {
    queueFront = NULL;
    queueSize = 0;
}

template<class T>
LinkedQueue<T>::~LinkedQueue() {
    while (queueFront) {
        chainNode<T> *nextNode = queueFront->next;
        delete queueFront;
        queueFront = nextNode;
    }
}

template<class T>
T &LinkedQueue<T>::front() {
    if (queueSize == 0)
        throw "error";
    return queueFront->element;
}

template<class T>
T &LinkedQueue<T>::back() {
    if (queueSize == 0)
        throw "error";
    return queueBack->element;
}

template<class T>
void LinkedQueue<T>::push(const T &theElement) {
    chainNode<T> *newNode = new chainNode<T>(theElement, NULL);
    if (queueSize != 0)
        queueBack->next = newNode;
    else queueFront = newNode;
    queueBack = newNode;
    queueSize++;
}

template<class T>
void LinkedQueue<T>::pop() {
    if (queueFront == NULL)
        throw "empty";
    chainNode<T> *nextNode = queueFront->next;
    delete queueFront;
    queueFront = nextNode;
    queueSize--;
}