双向链表堆栈删除功能不起作用

Question

我已经实现了双向链表来推送和弹出堆栈中的值。我的弹出功能不起作用。我已经对该程序进行了几次试运行，所有这些都在纸上运行。如果可能，请指导。

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 #include<iostream>
    #include<conio.h>
    #include<iomanip>

    using namespace std;

    struct node
    {
        node * prev;
        int val;
        node * next;    
    };

    class myStack
    {
        node * first;
        node * cur;
        node * prev0;

        public:
            myStack (): first(NULL), cur(NULL), prev0(NULL){}

            void push();

            void pop();

            void noutput();

            void output();

            ~myStack(){}
    };

    void myStack :: push()
    {
        cur = new node;
        cur->prev = NULL;
        cur->next = NULL;
        cout<<"Enter the Number to push in Stack :"<<endl;
        cin>>cur->val;
        cout<<endl;

        if(first == NULL)
        {
            first = prev0 = cur;
        }

        else
        {
            prev0->next = cur;
            cur->prev = prev0;
            prev0 = cur;

        }
    }

    void myStack :: pop()
    {       
        prev0 = cur->prev;
        delete cur;
        prev0->next = NULL;
        cur = prev0;
    }

    void myStack :: noutput()
    {
            cur = first;

            system("cls");
            cout<<setw(70)<<"NODE VIEW"<<endl;
            cout<<setw(55)<<"Prev"<<"        Cur"<<"       Next";
            cout<<endl<<endl;

            while(cur)
            {
                cout<<setw(55)<<cur->prev<<" | "<<cur<<" | "<<cur->next<<endl;
                cur = cur->next;
            }
            system("pause");
    }

    void myStack :: output()
    {
            cur = first;

            system("cls");

            cout<<setw(60)<<"STACK VIEW"<<endl<<endl;

            while(cur)
            {
                cout<<setw(55)<<" | "<<cur->val<<endl;
                cur = cur->next;
            }

            system("pause");
    }

    int main()
    {
        myStack q;
        char op;
        int key;

        for(int i = 0; i < 1; )
        {
            system("cls");
            cout<<"Press 1 to push value          :"<<endl;
            cout<<"Press 2 to pop value           :"<<endl;
            cout<<"Press 3 to Print Node View     :"<<endl;
            cout<<"Press 4 to Print Stack View    :"<<endl;
            cout<<"Press esc to exit              :"<<endl;

            op = _getch();
            key = op;

            if(key == 49)
            {
                q.push();
            }

            else if(key == 50)
            {
                q.pop();
            }

            else if(key == 51)
            {
                q.noutput();
                cout<<"\n\n";
            }

            else if(key == 52)
            {
                q.output();
                cout<<"\n\n";
            }

            else if(key == 27)
                i++;
            else
            {
                cout<<"\a Invalid Value Enter Again:"<<endl;
                system("pause");
            }   
        }
        system("pause");
        return 0;
    }

Answer 1

pop 方法存在处理栈中最后一项的问题。

void myStack :: pop()
{   
    if((first != null) && (first == prev0))
    {
        delete first;
        first = prev0 = cur = null;
    }
    else
    {
        prev0 = cur->prev;
        delete cur;
        prev0->next = NULL;
        cur = prev0;
    }
}