#include <iostream>
using namespace std;


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

struct DLCL {
    node * head, * tail;
    void init() {
        head = NULL;
        tail = NULL;
    }

    void insertFront(int x) {
        node * new_node = new node;
        new_node->info = x;
        new_node->next = NULL;
        new_node->prev = NULL;

        if(head == NULL) {
            head = new_node;
            tail = head;
            head->next = tail;
            tail->prev = head;
        }
        else {
            new_node->next = head;
            head->prev = new_node;
            head = new_node;
            tail->next = head;
            head->prev = tail;
        }

    }

    void insertEnd(int x) {
        node * new_node = new node;
        new_node->info = x;
        new_node->next = NULL;
        new_node->prev = NULL;

        if(head == NULL) {
            head = new_node;
            tail = head;
            head->prev = tail;
            tail->next = head;
        }
        else {
            tail->next = new_node;
            new_node->prev = tail;

            tail = new_node;
            tail->next = head;
            head->prev = tail;
        }
    }

    void deleteFront() {
        if(head != NULL) {
            if(head->next == head) {
                delete head;
                head = NULL;
                tail = NULL;
            }
            else {

                head = head->next;
                delete head->prev;
                head->prev = tail;
                tail->next = head;

            }
        }
    }

    void deleteEnd() {
        if(head != NULL) {
            if(head->next == head) {
                delete head;
                head = NULL;
                tail = NULL;
            }
            else {
                tail = tail->prev;
                delete tail->next;
                tail->next = head;
                head->prev = tail;
            }
        }
    }

    void deleteNode(int x) {
        if(head != NULL) {
            if(head->info == x) {
                deleteFront();
            }
            else {
                node * tmp = head;
                while(tmp->info != x) {
                    tmp = tmp->next;
                }
                if(tmp->next == head) {
                    deleteEnd();
                }
                else {
                    tmp->prev->next = tmp->next;
                    tmp->next->prev = tmp->prev;
                    delete tmp;
                }
            }
        }
    }
    void deleteNode(node *  x) {
        if(head != NULL) {
            if(head == x) {
                deleteFront();
            }
            else {
                node * tmp = head;
                while(tmp != x) {
                    tmp = tmp->next;
                }
                if(tmp->next == head) {
                    deleteEnd();
                }
                else {
                    tmp->prev->next = tmp->next;
                    tmp->next->prev = tmp->prev;
                    delete tmp;
                }
            }
        }
    }

    void inserAfter(int x, node * after) {
        node * new_node = new node;
        new_node->info = x;
        new_node->next = NULL;
        new_node->prev = NULL;

        if(after != NULL) {
            if(after == head) {
                insertFront(x);
            }
            else if(after == tail) {
                insertEnd(x);
            }
            else {

                new_node->next = after->next;
                new_node->prev = after;
                after->next = new_node;
                new_node->next->prev = new_node;
            }
        }
    }
    void print() {
        if(head != NULL) {
            node * tmp = head;
            while(tmp != tail) {
                cout << tmp->info << "-->";
                tmp = tmp->next;
            }
            cout << tmp->info<<"-->";
            tmp = tmp->next;
            while(tmp != tail) {
                cout << tmp->info << "-->";
                tmp = tmp->next;
            }
            cout << tmp->info << endl;

            while(tmp != head) {
                cout << tmp->info << "<--";
                tmp = tmp->prev;
            }
            cout << tmp->info << "<--";
            tmp = tmp->prev;
            while(tmp != head) {
                cout << tmp->info << "<--";
                tmp = tmp->prev;
            }
            cout << tmp->info << endl;
        }
    }

};
int main() {
    DLCL dll;
    dll.init();

    dll.insertFront(1);
    dll.insertFront(2);
    dll.insertFront(3);

    dll.insertEnd(4);
    dll.insertEnd(5);
    dll.insertEnd(6);
    dll.print();


    node * tmp = dll.head->next;
    dll.inserAfter(7, tmp);

    dll.print();

    return 0;
}