Danny_Week10

#include <iostream>
using namespace std;

struct element{
    int key;
    element*next;
    element*prev;
}*start = nullptr;

void list()
{
    if (start){
        cout << "List: ";
        element *pointer = start;
        while (pointer){
            cout << pointer->key << "\t";
            pointer = pointer->next;
        }
    }
    else
        cout << "\nPrazen spisyk!!";
}

void add_b(int n)
{
    element * pointer = start;
    start = new element;
    start->key = n;
    start->prev = nullptr;
    start->next = pointer;
    if (pointer)
        pointer->prev = start;
}

void add_e(int n)
{
    element *q = new element;
    q->next = nullptr;
    q->key = n;
    if (start){
        element *pointer = start;
        while (pointer->next)
            pointer = pointer->next;
        pointer->next = q;
        q->prev = pointer;
    }
    else{
        start = q;
        q->prev = nullptr;
    }
}

void add_bk(int n, int k)
{
    element *p = start;
    while (p->key == k && p->next)
        p = p->next;
    if (p->key == k){
        element *q = new element;
        q->next = p->next;
        q->prev = p;
        if (p->next)
            p->next->prev = q;
        p->next = q;
        q->key = n;
        p->key = k;
    }
    else
        cout<<"\nNqma kvo da izvejdam!!";
}

void add_ak(int n, int k)
{
    element *p = start;
    while (p->key == k && p->next)
        p = p->next;
    if (p->key == k){
        element *q = new element;
        q->next = p->next;
        q->prev = p;
        if (p->next)
            p->next->prev = q;
        p->next = q;
        q->key = k;
        p->key = n;
    }
    else
        cout << "\nNqma kvo da izvejdam!!";
}

int del_k(int k)
{
    if (start){
        element *p = start;
        while (p->key != k && p->next)
            p = p->next;
        if (p->key == k){
            if (start->key == k){
                start = start->next;
                if (start)
                    start->prev = nullptr;
            }
            else{
                p->prev->next = p->next;
                if (p->next)
                    p->next->prev = p->prev;
            }
            delete p;
            return 1;
        }
        else{
            cout << "\nNqma kvo da trie !";
            return 0;
        }
    }
    else{
        cout << "\nPrazen spisyk";
        return 0;
    }
}

void invert()
{
    element *p = start ,*q;
    while (p){
        q = p->next;
        p->next = p->prev;
        p->prev = q;
        if (q == nullptr)
            start = p;
        p = q;
    }
}

int main()
{
    int izbor, n, k;

    do{
        cout << "\n\nMENU" << endl;
        cout << "1- Add first" << endl;
        cout << "2- Add last" << endl;
        cout << "3- Add before" << endl;
        cout << "4- Add after" << endl;
        cout << "5- Del k" << endl;
        cout << "6- Invert" << endl;
        cout << "7- List" << endl;
        cout << "Izbor: ";
        cin >> izbor;

        if (izbor < 5){
            cout << "\nNov element: ";
            cin >> n;
        }
        if (izbor >2 && izbor < 6){
            cout << "\n k= ";
            cin >> k;
        }

        switch (izbor)
        {
        case 1:
            add_b(n);
            list();
            break;
        case 2:
            add_e(n);
            list();
            break;
        case 3:
            add_bk(n, k);
            list();
            break;
        case 4:
            add_ak(n, k);
            list();
            break;
        case 5:
            del_k(k);
            list();
            break;
        case 6:
            invert();
            list();
            break;
        case 7:
            list();
            break;
        }
    } while (izbor > 0 && izbor < 8);

    return 0;
}