struktura danych jak zrobić z next prev

struct ST //deklaracja struktury
{
	string nik;
	string haslo;
	string status;
	string rodzaj_konta;

	struct ST *next;
        struct ST *prev;
};

 
                ST POS1;
                POS1[0].nik = "alien0";
		POS1[0].haslo = "12340";
		POS1[1].nik = "alien1";
		POS1[1].haslo = "12341";
		POS1[2].nik = "alien2";
		POS1[2].haslo = "12342";

while (POS1->next) {
			textBox1->AppendText(gcnew String(POS1->haslo.c_str()));
		}

while (POS1->next()) {
			textBox1->AppendText(gcnew String(POS1->haslo.c_str()));
		}

struct ST //deklaracja struktury
{
    string nik;
    string haslo;
    string status;
    string rodzaj_konta;
 
    struct ST *next;
    struct ST *prev;

    ST()
    {
      next = 0;
      prev = 0;
    }
    void push_back(ST * element)
    {
       next = element;
       element->prev = this;
    }
};

ST element_0;
ST element_1;
ST element_2;
element_0.nik = "alien0";
element_0.haslo = "12340";
element_1.nik = "alien1";
element_1.haslo = "12341";
element_2.nik = "alien2";
element_2.haslo = "12342";

element_0.push_back(element_1);
element_1.push_back(element_2);

ST * node = element_0;
while (node = node->next) 
{
  textBox1->AppendText(gcnew String(node->haslo.c_str())); // tutaj masz memory leaka jeśli textBox1 sam nie usunie tego Stringa.
}

for(ST * node = element_0;node;node=node->next)  textBox1->AppendText(gcnew String(node->haslo.c_str())); // nie ma tu żadnego memory leaka

ref struct ST //deklaracja struktury
{
    String ^nik;
    String ^haslo;
    String ^status;
    String ^rodzaj_konta;
 
    ref struct ST ^next;
    ref struct ST ^prev;
};

element_0.push_back(element_1);
element_1.push_back(element_2);

element_0.push_back(&element_1);
element_1.push_back(&element_2);