C++ - 模板类堆栈实现中的反向函数

Question

这是我使用带有结构类型节点和类类型堆栈的模板的堆栈实现:

---

堆栈.h

#ifndef STACK_H_
#define STACK_H_

#include <cstdlib>
#include <iostream>
#include <cassert>

using namespace std;

template <class t>
struct node{
    t data;
    node<t>* next;
};

template <class t>
class stack
{
public:
    stack();
    ~stack();
    bool isEmpty(){ return (top_ptr=NULL);};
    void push(const t&);
    void pop();
    t top() const;
    void reverse();
    void clear();
    void print();
private:
    node<t>* top_ptr;
};

template <class t>
stack<t>::stack()
{
    top_ptr=NULL;
}

template <class t>
stack<t>::~stack()
{
    while(top_ptr != NULL) pop();
}

template <class t>
void stack<t>::push(const t& source)
{
    node<t>* new_node = new node<t>;
    new_node->data = source;
    new_node->next = top_ptr;
    top_ptr = new_node;
    cout << "Inserito!" << endl;
}

template <class t>
void stack<t>::pop()
{
    node<t>* remove = top_ptr;
    top_ptr = top_ptr->next;
    delete remove;
    cout << "Rimosso!" << endl;
}

template <class t>
t stack<t>::top() const
{
    assert(top_ptr != NULL);
    return top_ptr->data;
}

template <class t>
void stack<t>::clear()
{
    node<t>* temp;
    while(top_ptr != NULL)
    {
        temp = top_ptr;
        top_ptr = top_ptr->next;
        delete temp;
    }
    cout << "Clear completato!" << endl;
}

template <class t>
void stack<t>::reverse()
{
    stack<t> new_stack;
    while(top_ptr != NULL)
    {
        new_stack.push(top_ptr->data);
        pop();
    }
    cout << "Reverse completato!" << endl;
}

template <class t>
void stack<t>::print()
{
    node<t>* ptr = top_ptr;
    while(ptr!=NULL)
    {
        cout << " " << ptr->data << endl;
        ptr = ptr->next;
    }
}

#endif /* STACK_H_ */

---

这是 main.cpp:

#include "stack.h"

int main()
{
    stack<int> stackino;
    for(int i = 0; i<10; i++) stackino.push(i);
    stackino.pop();
    cout << "top(): " << stackino.top() << endl;
    stackino.print();
    cout << "Invoco clear()" << endl;
    stackino.clear();
    cout << "Stackino dopo clear():" << endl;
    stackino.print();
    cout << "Invoco reverse()" << endl;
    stackino.reverse();
    cout << "Stackino dopo reverse()" << endl;
    stackino.print();

    cout << "FINE!" << endl;
    return 0;
}

---

问题是 reverse() 导致程序崩溃，我猜“top_ptr = new_stack.top_ptr”是错误的但它编译和执行，但崩溃。有人可以帮我改正吗？

Answer 1

我想我理解了这个问题。如果我解释错了，请告诉我。当您执行 top_ptr = new_stack.top_ptr 时，您将把临时堆栈的顶部作为您的。问题是，当那个临时堆栈被破坏时，它仍然有相同的 top_ptr，并删除所有与之关联的内存。这会使您的真实堆栈出现错误的 top_ptr。

我建议尝试:

top_ptr = new_stack.top_ptr;
new_stack.top_ptr = NULL;

这样它就不会清除您的堆栈，并给您留下一个错误的指针。希望有用吗？