#include #include void add_to_list(list_t *head, list_t *prev, list_t *next) { head->prev = prev; head->next = next; prev->next = head; next->prev = head; } void free_node(list_t *head) { if (list_is_empty(head)) { head = NULL; return; } head->next->prev = head->prev; head->prev->next = head->next; head = NULL; }