Question

我在双链表中添加节点部分需要帮助。我干了我的程序看起来很完美但它在添加第二个或第三个节点时崩溃了。我想要一个合乎逻辑的理由为什么会这样。任何人？这是我的代码。

class node
    {
    public:
        int data;
        node* next;
        node* previous;
    };

    class linklist
    {
    private:
        node* current;
        node* head;
        node* tail;
        int count;
        int size;

    public:
        linklist() : head(NULL), tail(NULL), size(1) {}

    void addNthNode(int Data, unsigned int position)
        {
            node* currentNew = new node;
            currentNew->data = Data;

            if (position == 1)
            {
                currentNew->next = head;
                currentNew->previous = NULL;
                head = currentNew;
                return;
            }

            node* temp1 = head;
            for (int i = 1; i < position - 1; i++)
                temp1 = temp1->next;

            node* temp2 = temp1->next;

            currentNew->previous = temp1;
            currentNew->next = temp2;
        }

    int getSizeOfList()
        {
            node* temp = head;
            while (temp->next != NULL)
            {
                temp = temp->next;
                ++size;
            }
            return size;
        }

    void main()
    {
        linklist l;

        l.addNthNode(1, 1);
        l.addNthNode(2, 2);
        l.addNthNode(3, 3);

        l.printList();
        cout << "\nSize of list : " << l.getSizeOfList() << endl << endl;

    }

Answer 1

插入新节点时，您不会更新所选位置的任何现有节点的next和previous字段，因此它们指向新节点。您也没有递增列表的count和size字段，也不会在列表末尾插入时更新其tail字段。

请改为尝试：

class node
{
public:
    int data;
    node* next;
    node* previous;

    node(int value = 0) : data(value), next(NULL), previous(NULL) {}
};

class linklist
{
private:
    node* head;
    node* tail;
    int size;

public:
    linklist() : head(NULL), tail(NULL), size(0) {}

    void addNthNode(int Data, unsigned int position)
    {
        node* currentNew = new node(Data);

        if (position <= 1)
        {
            currentNew->next = head;
            if (head)
                head->previous = currentNew;
            head = currentNew;
        }

        if (position >= size)
        {
            currentNew->previous = tail;
            if (tail)
                tail->next = currentNew;
            tail = currentNew;
        }

        if ((position > 1) && (position < size))
        {
            node *temp = head;
            while (position-- > 1)
                temp = temp->next;

            currentNew->next = temp;

            if (temp->previous)
                temp->previous->next = currentNew;
            temp->previous = currentNew;
        }

        ++size;
    }

    int getSizeOfList()
    {
        return size;
    }

    void printList()
    {
        //...
    }
};

int main()
{
    linklist l;

    l.addNthNode(1, 1);
    l.addNthNode(2, 2);
    l.addNthNode(3, 3);

    l.printList();
    std::cout << "\nSize of list : " << l.getSizeOfList() << std::endl << std::endl;

    return 0;
}

话虽如此，您应该认真考虑使用std::list而不是手动实现：

#include <list>

class linklist
{
private:
    std::list<int> l;

public:
    void addNthNode(int Data, unsigned int position)
    {
        std::list<int>::iterator iter = l.begin();
        std::advance(iter, position-1);
        l.insert(iter, Data);
    }

    int getSizeOfList()
    {
        return l.size();
    }

    void printList()
    {
        //...
    }
};

int main()
{
    linklist l;

    l.addNthNode(1, 1);
    l.addNthNode(2, 2);
    l.addNthNode(3, 3);

    l.printList();
    std::cout << "\nSize of list : " << l.getSizeOfList() << std::endl << std::endl;

    return 0;
}

在第n个位置添加节点的双链表

1 个答案: