연결리스트 연산들

typedef int element;


typedef struct ListNode {
	element data;
	struct ListNode* link;
}ListNode;


ListNode* insert_first(ListNode* head, int value) {
	ListNode* p;
	p = (ListNode*)malloc(sizeof(ListNode));
	p->data = value;
	p->link = head;
	head = p;

	return head;
}

ListNode* insert(ListNode* head, ListNode* pre, element value) {

	ListNode* p;
	p = (ListNode*)malloc(sizeof(ListNode));
	p->data = value;
	p->link = pre->link;
	return head;
}

void print_list(ListNode* head) {
	ListNode* p;
	p = head;
	while (p != NULL) {
		printf("%d\n", p->data);
		p = p->link;
	}
	
}

ListNode* delete_first(ListNode* head) {
	ListNode* removed;
	if (head != NULL) {
		removed = head;
		head = removed->link;
		free(removed);
	}
	return head;
}

ListNode* delete(ListNode* head, ListNode* pre) {
	ListNode* removed;
	removed = pre->link;
	pre->link = removed->link;
	free(removed);

	return head;
}

int main(void) {
	ListNode* head = NULL;

	for (int i = 0; i < 5; i++) {
		head = insert_first(head, i);
		print_list(head);
	}

	for (int i = 0; i < 5; i++) {
		head = delete_first(head);
		print_list(head);
	}

	return 0;
}