Question

我一直在为我的析构函数开发一个链表项目，其中偶数插入前面，奇数插入后面。删除工作在后进先出，取决于它是奇数还是偶数。我有一切正常，但是当我运行析构函数时，我一直收到错误。我已经完成了调试并删除了所有节点，但随后崩溃了，我不知道为什么。这是我的代码：

//Headerfile
class Staque
{
private:
struct staqueNode
{
    int value;
    struct staqueNode *next;
    struct staqueNode *prev;
};

staqueNode *root;


public:
Staque();
~Staque();

void addNode(int addIn);
void deleteNode(int oddIn, int evenIn);
void display();
};

//header.cpp file
#include"Staque.h"
#include<iostream>

using namespace std;

Staque::Staque()
{
root = NULL;    
}

void Staque::addNode(int addIn)
{
staqueNode *newNode;
staqueNode *nodePtr;
staqueNode *temp = NULL;

newNode = new staqueNode;
newNode->value = addIn;
newNode->next = NULL;
newNode->prev = NULL;
if (!root)
{
    root = newNode;
}
else
{
    if (newNode->value % 2 == 0)
    {
        nodePtr = root;
        while (nodePtr->next)
        {
            nodePtr = nodePtr->next;
        } 
        nodePtr->next = newNode;
        newNode->prev = nodePtr;
    }
    else if (newNode->value % 2 != 0)
    {
        nodePtr = root;
        while (nodePtr->prev)
        {
            nodePtr = nodePtr->prev;
        }
        nodePtr->prev = newNode;
        newNode->next = nodePtr;
    }
}
} 
void Staque::deleteNode(int oddIn, int evenIn)
{
staqueNode *nodePtr;
staqueNode *temp = NULL;
if (!root)
    return;
while (evenIn > 0)
{
    nodePtr = root;
    while (nodePtr != NULL && nodePtr->next != NULL)
    {
        temp = nodePtr;
        nodePtr = nodePtr->next;
    }
    if (nodePtr == root && root->value % 2 == 0)
    {
        root = root->prev;
        temp->next = NULL;
        delete nodePtr;
        evenIn = 0;
    }
    else
    {
        temp->next = NULL;
        delete nodePtr;
        evenIn -= 1;
    }
}

while (oddIn > 0)
{
    nodePtr = root;
    while (nodePtr != NULL && nodePtr->prev != NULL)
    {
        temp = nodePtr;
        nodePtr = nodePtr->prev;
    }
    if (nodePtr == root && root->value % 2 != 0)
    {
        root = root->next;
        temp->prev = NULL;
        delete nodePtr;
        oddIn = 0;
    }
    else
    {
        temp->prev = NULL; 
        delete nodePtr;
        oddIn -= 1;
    }
}

}

void Staque::display()
{
staqueNode *nodePtr;

nodePtr = root;
while (nodePtr->next)
{   
    nodePtr = nodePtr->next;
}
cout << "\nThe staque: ";
while (nodePtr->prev)
{
    cout << nodePtr->value << " ";
    nodePtr = nodePtr->prev;
}
cout << nodePtr->value << endl;

}

Staque::~Staque()
{
staqueNode *nodePtr;
staqueNode *temp;
nodePtr = root;

while (nodePtr->next)
{
    temp = nodePtr;
    nodePtr = nodePtr->next;
}
//nodePtr = root;
while (nodePtr->prev)
{
    temp = nodePtr;
    nodePtr = nodePtr->prev;
    delete temp;
}
//delete root;

}


//source/main.cpp
#include"Staque.h"
#include<iostream>


using namespace std;

int main()
{
Staque myList;
int choice;
int input;
int numOdd;
int numEven;

do
{
    cout << "Would you like to: \nAdd a node: 1\nDelete a node: 2\nDisplay the list: 3\nQuit: 0\n";
    cin >> choice;
    while (choice < 0 || choice > 3)
    {
        cout << "Invalid Input: Would you like to: \nAdd a node: 1\nDelete a node: 2\nDisplay the list: 3\nQuit: 0\n";
        cin >> choice;
    }
    switch (choice)
    { 
    case 1:
        cout << "Enter the value you would like to add to the list: ";
        cin >> input;
        while (isalpha(input))
        {
            cout << "Invalid input: Enter the value you would like to add to the list: ";
            cin >> input;
        }
        myList.addNode(input);
        myList.display();
        break;

    case 2:
        cout << "Enter the number of even numbers you would like to delete: ";
        cin >> numEven;
        while (isalpha(input) || numEven < 0)
        {
            cout << "Invalid input: Enter the number of even numbers you would like to delete: ";
            cin >> numEven;
        }

        cout << "Enter the number of odd numbers you would like to delete: ";
        cin >> numOdd;
        while (isalpha(input) || numEven < 0)
        {
            cout << "Invalid input: Enter the number of odd numbers you would like to delete: ";
            cin >> numOdd;
        }
        myList.deleteNode(numOdd, numEven);
        myList.display();
        break;

    case 3:
        myList.display();
        break;

    default:
        break;

    }
} while (choice != 0);

myList.~Staque();

return 0;

}

Answer 1

一个明显的错误是你明确地调用了析构函数。

myList.~Staque();

你不应该这样做 - 当物体超出范围时，物体将自然地“死亡”。通过显式调用析构函数，该对象将调用析构函数，然后在对象超出作用域时第二次调用析构函数。这是第二次调用会导致所有破坏。

你应该明确调用析构函数的时间是你正在使用placement-new，而你在这里没有这样做。因此，只需删除上面的那一行，看看错误是否消失。如果没有，那么您还有其他问题，但至少，您会从代码中删除这个明显的问题。

Answer 2

专门看你的析构函数......

nodePtr为null时会发生什么？例如，您没有创建节点。

或者你到达最后一个节点，它总是将下一个ptr设置为NULL，然后在空指针上取消引用nodePtr-＆gt; - 是的，你猜它是一个崩溃。

在你的while（nodePtr-＆gt; next）什么是临时任务呢？看起来没什么用。

while（nodePtr-＆gt; prev）???

不检查nodePtr是否为空？

首先要做的事情。

您是否确定其余部分有效？

Linked-list析构函数崩溃了C ++程序

2 个答案: