c++ - 向链表的末尾添加值并从前面删除 C++

Question

我正在尝试将项目添加到列表的末尾并从列表的开头删除它们。该程序编译但在我尝试添加项目时崩溃。我是这个概念的新手，需要一些时间才能完全适应。任何帮助表示赞赏.. 谢谢!

  #include<iostream>
using namespace std;



struct myNode
{
    int val;
    struct myNode *next;
};


class Cll
{

public:
    myNode* head = new myNode;
    myNode* tail = new myNode;

    Cll()
    {
        head = NULL;
        tail = NULL;
    }
    myNode* createAnode(int value)
    {
        myNode* temp;
        temp = new myNode;

        temp->val = value;
        temp->next = NULL;
        return temp;
    }
    void addingValues()
    {
        int numb;
        cout<<"Enter the number to be added: ";
        cin>>numb;
        myNode *temp, *p;
        temp = createAnode(numb);

        p = head;
        p = p-> next;
       temp -> next = NULL ;
        p -> next = temp;

    }
        void deletingValues()
    {
        myNode *s;
        s = head;
        head = s->next;
    }

     void showValues()
    {
        struct myNode *temp2;

        temp2 = head;
        while (temp2)
        {
            cout<<temp2->val<<"->";
            temp2 = temp2->next;
        }
        cout<<"NULL"<<endl;
    }

};



int main()
{

    int pick ;
    Cll cll;
    int again;




    do
    {

        cout<<"1.add"<<endl;
        cout<<"2.delete"<<endl;
        cout<<"3.show"<<endl;
        cout<<"Enter choice : ";
        cin>>pick;
        switch(pick)
        {
            case 1:
                cll.addingValues();
                cout<<endl;
                break;

            case 2:
                cll.deletingValues();
                break;
            case 3:
                cll.showValues();
                cout<<endl;
                break;

        }
        cout << "Enter 1 to see again, enter 2 to quit"<< endl;
        cin >> again;

    } while (again == 1);




}

Answer 1

您正在使用 C++ 编程，所以我建议使用 std::list。

但是如果你喜欢自己做，喜欢在你的单个喜欢列表前面添加一个节点，你首先要检查它是否是第一个节点。 如果它是第一个节点，则您的新节点是 head 和 tail。如果不是，则新节点是表头，其后继者是列表的旧表头。像这样调整您的代码:

void addingValues()
{
    int numb;
    cout << "Enter the number to be added: ";
    cin >> numb;
    myNode  *newNode = createAnode(numb);

    if ( head == NULL ) // if list is empty the new node is the head and the tail
    {
        head = tail = newNode;
        return;
    }

    tail->next = newNode; // successor of last node is new node and new node is tail
    tail = newNode;
}

要从列表前面删除一个节点，您必须检查列表是否不为空以及它是否是列表中的最后一个节点:

void deletingValues()
{
    if ( head == NULL )
        return;

    myNode *temp = head->next;
    delete head;
    head = temp;
    if ( head == NULL )
        tail == NULL;
}