🅐 p->next->prev = s; s->prev = p; p->next = s; s->next = p->next; 🅑 p->next->prev = s; p->next = s; s->prev = p; s->next = p->next; 🅒 s->prev = p; s->next = p->next; p->next = s; p->next->prev = s; 🅓 s->next = p->next; p->next->prev = s; s->prev = p; p->next = s;