#include <iostream>
#include <set>
using namespace std;
class List {
public:
    List() {
        create_List();
        }
    ~List() {
        clear();
    }
    void create_List();
    void clear();
    void print();
    void reverse();
    void insert(const int &d);
    void add(const int& d);
private:
    struct ListNode {
        int val;
        ListNode* next;
        ListNode(const int& d) :val(d), next(nullptr) {}
    };

    ListNode* head;
};


void List:: clear() {
    
    ListNode* p = head;
    while (p)
    {
        ListNode* q = p->next;
        delete p;
        p = q;
    }
}

void List::insert(const int& d) {
    ListNode* p = new ListNode(d);
    p->next = head->next;
    head->next = p;
}


void List:: add(const int & d)
{
    ListNode* phead = head;
    while (phead->next)
    {
        phead = phead->next;
    }

    ListNode *p = new ListNode(d);
    phead->next = p;
}


void List::print() {
    for (ListNode* p = head->next; p; p = p->next) {
        cout << p->val << endl;
    }
}

void List::reverse() {
    ListNode* p = head->next;
    ListNode* q = head->next->next;
    ListNode* m = head->next->next->next;
    p->next = nullptr;
    while (m)
    {
        q->next = p;
        p = q;
        q = m;
        m = m->next;
    }
    q->next = p;
    head->next = q;
}

//创建头结点
void List::create_List(){
    head = new ListNode(0);
}


int main()
{
    List List;
   // List.insert(30);
    //List.insert(20);
   // List.insert(40);
    List.add(10);
    List.add(20);
    List.add(30);
    List.print();
    List.reverse();
   List.print();

    //test();
}