Lista Jednokierunkowa

#include <iostream>
#include <time.h>
#include <stdio.h>

using namespace std;

struct element {
int data;
element* next;
};
struct lista {
element* head;
element* tail;
int el_count;
};

lista create_list ();
void add_tail(lista &l, int r_d);
void add_head(lista &l, int r_d);
void add_position(lista &l, int r_d, int posit);
void delete_tail(lista &l);
void delete_head(lista &l);
void delete_position(lista &l, int posit);
void delete_list(lista &l);
void show_list(lista l);
void show_on_position(lista l, int posit);


int main()
{
    lista l = create_list();
    int wybor, posit;
    cout << "Podaj pozycje" << endl;
    cin >> posit;
    srand(time(NULL));
    do{
cout << "Podaj wybor:" << endl;
cout << "1. Dodawanie elementu o losowej wartosci na koniec listy " << endl;
cout << "2. Dodawanie elementu o losowej wartosci na poczatek listy " << endl;
cout << "3. Dodawanie elementu o losowej wartosci na pozycje o podanym numerze " << endl;
cout << "4. Usuniecie elementu z konca listy " << endl;
cout << "5. Usuniecie elementu z poczatku listy" << endl;
cout << "6. Usuniecie elementu z podanej pozycji" << endl;
cout << "7. Wyswietlenie elementu o podanym numerze" << endl;
cout << "8. Wyswietlenie calej listy" << endl;
cout << "9. Usuniecie wszystkich elementow listy wraz ze zwolnieniem pamieci" << endl;
cout << "10. Wyjscie" << endl;
cout << "Odpowiedz:" << endl;
cin >> wybor;
switch(wybor){
case 1: add_tail(l, rand()); break;
case 2: add_head(l, rand()); break;
case 3: add_position(l, rand(), posit); break;
case 4: delete_tail(l); break;
case 5: delete_head(l); break;
case 6: delete_position(l, posit); break;
case 7: show_on_position(l, posit); break;
case 8: show_list(l); break;
case 9: delete_list(l); break;
case 10: cout << "Wyszedles z progrmau" << endl;  break;
default : cout << "bledny wybor" << endl; break;


}
    } while (wybor != 10);
    return 0;
}

lista create_list (){
lista new_list;
new_list.head = nullptr;
new_list.tail = nullptr;
new_list.el_count = 0;
return new_list;}

void add_tail(lista &l, int r_d){
cout << "Lista biezaca:" << endl;
show_list(l);
cout << "Numer ktory zostanie dodany: " << r_d << endl;
element* n_tail = new element;
n_tail -> data = r_d;
n_tail -> next = nullptr;

if(l.tail != nullptr)
    l.tail -> next = n_tail;
else
    l.head = n_tail;
l.tail = n_tail;
l.el_count ++;
cout << "Lista po zmianie:" << endl;
show_list(l);
}

void add_head(lista &l, int r_d){
cout << "Lista biezaca:" << endl;
show_list(l);
cout << "Numer ktory zostanie dodany: " << r_d << endl;
element* n_head = new element;
n_head -> data = r_d;
n_head -> next = l.head;
l.head = n_head;

if(l.tail == nullptr)
    l.tail == n_head;
l.el_count ++;
cout << "Lista po zmianie:" << endl;
show_list(l);
}

void add_position(lista &l, int r_d, int posit){
cout << "Lista biezaca:" << endl;
show_list(l);
cout << "Numer ktory zostanie dodany: " << r_d << endl;
if(posit <0 or posit > l.el_count) return;
if(posit == 0)
    {
    add_head(l, r_d);
    return;
    }
if(posit == l.el_count)
    {
    add_tail(l, r_d);
    return;
    }
element* temp = l.head;
for(int i=0; i < posit -1; i++)
    temp = temp -> next;
element* n_e = new element;
n_e -> data = r_d;
n_e -> next = temp -> next;
temp -> next = n_e;
l.el_count ++;
cout << "Lista po zmianie:" << endl;
show_list(l);
}


void delete_tail(lista &l){
cout << "Lista biezaca:" << endl;
show_list(l);
if(l.tail == nullptr) return;
element* temp = l.tail;
if(l.el_count == 1)
    {
    l.tail == nullptr;
    l.head == nullptr;
    }
else{
element * tempor = l.head;
for (int i =1; i< l.el_count -1; i++)
    {
    tempor = tempor -> next;
    }
l.tail = tempor;
l.tail -> next = nullptr;
    }
l.el_count --;
delete temp;
cout << "Lista po zmianie:" << endl;
show_list(l);
}

void delete_head(lista &l){
if(l.tail == nullptr) return;
cout << "Lista biezaca:" << endl;
show_list(l);
element* temp = l.head;
l.head = l.head -> next;
delete temp;
if(l.head  == nullptr)
    l.tail = nullptr;
cout << "Element z poczatku zostal usuniety" << endl;
l.el_count--;
cout << "Lista po zmianie:" << endl;
show_list(l);
}

void delete_position(lista &l, int posit){
if (posit < 0 or posit > l.el_count)
        {
            cout << "Podano niewlasciwa pozycje" << endl;
        return;
        }
cout << "Lista biezaca:" << endl;
show_list(l);
if (posit == 0)
    {
    delete_head(l);
    return;
    }
if(posit == l.el_count)
    {
    delete_tail(l);
    return;
    }
element* temp = l.head;
for (int i =1; i< l.el_count -1; i++)
    {
    temp = temp -> next;
    }
element* temp_delete = temp -> next;
temp -> next = temp_delete -> next;
delete temp_delete;
l.el_count --;
cout << "Lista po zmianie:" << endl;
show_list(l);
}

void delete_list(lista &l){
while(l.head != nullptr){
    delete_head(l);
}
}

void show_list(lista l){
    element* temp = l.head;
while (temp)
    {
    cout << temp -> data << endl;
    temp = temp -> next;
    l.el_count --;
    }
}

void show_on_position(lista l, int posit)
{
int c = 0;
if (posit < 0 or posit > l.el_count)
        {
            cout << "Podano niewlasciwa pozycje" << endl;
        return;
        }
element* temp = l.head;
while(l.el_count != 0){
    c++;
    if (c == posit) cout << temp -> data << endl;
    temp = temp -> next;
    l.el_count --;
            }
}