+ if (index == 0) {
+ return list_prepend(head, value);
+ } else if (index == list_count(head)) {
+ return list_append(head, value);
+ } else {
+ link_t* link_insrt = list_new(value);
+ link_t* head_first = head;
+ link_t* head_next = NULL;
+ for (unsigned i = 0; i < index-1; i++) {
+ head = head->next;
+ }
+ head_next = head->next;
+ head->next = link_insrt;
+ head = link_insrt;
+ head->next = head_next;
+ return head_first;