数据结构基础(13) --链式栈的设计与实现

    采用链式存储的栈成为链式栈(或简称链栈), 链栈的优点是便于多个栈共享存储空间和提高其效率, 且不存在栈满上溢的情况(因为链栈是靠指针链接到一起,只要内存够大, 则链栈理论上可以存储的元素是没有上限的);

    与顺序栈相比, 由于顺序栈是采用的数组实现, 因此一旦数组填满, 则必须重新申请内存, 并将所有元素”搬家”, 而链栈则省略了这一”耗时耗力”的工作, 但却需要付出附加一个指针的代价;

    链栈通常采用单链表实现, 并规定所有的操作都必须实在单链表的表头进行, 而且w我们的链栈没有头结点, m_top直接指向栈顶元素;

链式栈的图示如下:

链栈节点构造:

template <typename Type>
class ChainNode
{
    template <typename T>
    friend ostream &operator<<(ostream &os, const LinkStack<T> &stack);
    friend class LinkStack<Type>;
private:
    ChainNode(const Type &_data, ChainNode *_next = NULL)
        :data(_data), next(_next) {}

    Type data;
    ChainNode *next;
};

链栈设计:

template <typename Type>
class LinkStack
{
    template <typename T>
    friend ostream &operator<<(ostream &os, const LinkStack<T> &stack);
public:
    LinkStack(): m_top(NULL) {}
    ~LinkStack()
    {
        makeEmpty();
    }
    bool isEmpty() const
    {
        return m_top == NULL;
    }

    void pop() throw(std::out_of_range);
    const Type &top() const throw(std::out_of_range);
    void push(const Type &data);
    void makeEmpty();

private:
    ChainNode<Type> *m_top;
};

栈的三大操作:

template <typename Type>
const Type &LinkStack<Type>::top() const
throw (std::out_of_range)
{
    if (isEmpty())
        throw std::out_of_range("stack is empty, can`t get data");

    return m_top->data;
}

template <typename Type>
void LinkStack<Type>::pop()
throw (std::out_of_range)
{
    if (isEmpty())
        throw std::out_of_range("stack is empty, can`t delete");

    ChainNode<Type> *deleteNode = m_top;
    m_top = m_top->next;
    delete deleteNode;
}

template <typename Type>
void LinkStack<Type>::push(const Type &data)
{
    //此处是整个链栈的关键点
    // 该操作会生成一个节点,
    // 并自动将m_top上移一格,
    // 而且将m_top原先指向的节点, 作为新生成的节点的下一节点
    //注意此处
    //如果第一次运行push, 则原m_top为NULL
    // 新m_top指向第一个元素
    m_top = new ChainNode<Type>(data, m_top);
}

清空整个栈:

template <typename Type>
void LinkStack<Type>::makeEmpty()
{
    while (!isEmpty())
    {
        pop();
    }
}

输出栈内所有内容:

template <typename Type>
ostream &operator<<(ostream &os, const LinkStack<Type> &stack)
{
    ChainNode<Type> *currentNode = stack.m_top;
    while (currentNode != NULL)
    {
        cout << currentNode->data << ' ';
        currentNode = currentNode->next;
    }

    return os;
}

测试代码:

int main()
{
    LinkStack<int> test;
    for (int i = 0; i < 10; ++i)
    {
        test.push(rand()%100);
    }

    cout << test << endl;
    cout << "top = " << test.top() << endl;

    test.pop();
    cout << "top = " << test.top() << endl;

    test.push(1);
    cout << "top = " << test.top() << endl;

    while (!test.isEmpty())
    {
        test.pop();
    }
    cout << test << endl;

    test.push(11);
    test.push(22);
    test.push(33);
    cout << test << endl;
    test.makeEmpty();

    try
    {
        cout << "top = " << test.top() << endl;
    }
    catch (const std::exception &e)
    {
        cerr << e.what() << endl;
    }

    return 0;
}