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Linked List Mayhem!

koko82 (24)
Hi All

Just learning about linked list and doing some excersises feel like I have hit a brick wall. There are two things one is when you self reference within a struct and then return does that link to the entire pointer to the struct for example p_head?

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struct EnemySpaceShip

{
    
    string ship_name;
    int x_coordinate;
    int y_coordinate;
    int weapon_power;
    EnemySpaceShip* p_next_enemy;
    
};

EnemySpaceShip* p_head = NULL;

EnemySpaceShip* getNewEnemy (string name)
{
    
    EnemySpaceShip* p_ship = new EnemySpaceShip;
    p_ship->ship_name = name;
    p_ship->x_coordinate = 0;
    p_ship->y_coordinate = 0;
    p_ship->weapon_power = 0;
    p_ship->p_next_enemy = p_head;
    p_head = p_ship;   
    return p_ship;
}


The other is don't understand how the same value makes two different results. Am I missing some fundamentals here?

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  next = current->p_last_enemy; // cout produces 0x1001054f0
  current->p_last_enemy = prev; // cout produces 0x100105570


Any help would be greatly appreciated.
closed account (SECMoG1T)
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next = current->p_last_enemy; // cout produces 0x1001054f0
 current->p_last_enemy = prev; // cout produces 0x100105570

Dint see them in your code plz add the full code
koko82 (24)
Hi heres the full code

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#include <iostream>

using namespace std;

struct EnemySpaceShip
{
    
    string ship_name;
    int x_coordinate;
    int y_coordinate;
    int weapon_power;
    EnemySpaceShip* p_next_enemy;
    EnemySpaceShip* p_last_enemy;
    EnemySpaceShip* p_current_enemy;
    
};

EnemySpaceShip* p_enemies = NULL;
EnemySpaceShip* p_enemies1 = NULL;

EnemySpaceShip* getNewEnemy (string name)
{
    
    EnemySpaceShip* p_ship = new EnemySpaceShip;
    p_ship->ship_name = name;
    p_ship->x_coordinate = 0;
    p_ship->y_coordinate = 0;
    p_ship->weapon_power = 0;
    p_ship->p_next_enemy = p_enemies;
    p_ship->p_last_enemy = p_enemies1;
    p_ship->p_current_enemy = p_ship;
    p_enemies = p_ship;
    p_enemies1 = p_ship;
    return p_ship;
}


void display_list(EnemySpaceShip *p_list)
{
    
    EnemySpaceShip *p_current = p_list;
   // p_current = p_current->p_next_enemy;
    
    while(p_current!=NULL)
        
    {
        cout << " Ship Name : " << p_current->ship_name << " Current Address : " << p_current->p_current_enemy << "      Previous Enemy : " <<
        p_current->p_next_enemy << "            Next Address : " << p_current->p_last_enemy << "\n";
        
        p_current = p_current->p_next_enemy;
        
        
    }
}

EnemySpaceShip* Reverse (struct EnemySpaceShip* head)
{
    EnemySpaceShip *current, *prev, *next;
    
    current = head;
    prev = NULL;
    
    while (current != NULL)
    {
        
        next = current->p_last_enemy;
        current->p_last_enemy = prev;
        prev = current;
        current = next;
    }
    
    head = prev;
    return head;
}


int main ()
{

    string sships[]= { "ship1", "ship2", "ship3", "ship4", "ship5", "ship6", "ship7" };
    EnemySpaceShip* p_ship1 = getNewEnemy(sships[0]);
    EnemySpaceShip* p_ship2 = getNewEnemy(sships[1]);
    EnemySpaceShip* p_ship3 = getNewEnemy(sships[2]);
    EnemySpaceShip* p_ship4 = getNewEnemy(sships[3]);
    EnemySpaceShip* p_ship5 = getNewEnemy(sships[4]);
    EnemySpaceShip* p_ship6 = getNewEnemy(sships[5]);
    EnemySpaceShip* p_ship7 = getNewEnemy(sships[6]);
    
    display_list(p_enemies);
    cout << "--------------- \n";
    Reverse(p_enemies1);
    display_list(p_enemies1);
    
}
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