insert after n

listn.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct _list {
	int value;
	
	struct _list *next;
} list;

int get_list_len(list *head) {
	int len=0;
	while (head != NULL) {
		head = head->next;
		len++;
	}
	
	return len;
}

void list_append(list *head, list *item) {
	while (head->next != NULL) {
		head = head->next;
	}
	
	head->next = item;
}

void insert_after_n(list *head, list *item, int n) {
	int len, i;
	
	len = get_list_len(head);
	
	if (len >= n) {
		for (i=1; i < n; i++) {
			head = head->next;
		}
		
		item->next = head->next;
		head->next = item;
	} else {
		list_append(head, item);
	}
}

/*TEST ONLY*/
list *create_item(int value) {
	list *item;
	
	item = (list *)malloc(sizeof(list));
	//if null die
	
	item->value = value;
	item->next = NULL;
	
	return item;
}

/*TEST ONLY*/
void list_print(list *head) {
	while (head) {
		printf("%d ", head->value);
		head = head->next;
	}
}

/*TEST ONLY*/
void list_delete(list *head) {
	list *next;
	
	while (head) {
		next = head->next;
		free(head);
		head = next;
	}
}

/*TEST ONLY*/
int main() {
	list *head;
	
	head = create_item(0);
	insert_after_n(head, create_item(1), 2);
	insert_after_n(head, create_item(2), 3);
	insert_after_n(head, create_item(4), 4);
	insert_after_n(head, create_item(5), 5);
	
	insert_after_n(head, create_item(3), 3);
	
	list_print(head);
	
	list_delete(head);
	
	printf("\n");

    return 0;
}