linkedlist.c

struct t_node {
    struct t_node *next;
    int value;
} t_node;

struct t_list {
    t_node *head;
    t_node *tail;
    int size;
} t_list;

void insert_node(t_list *list, t_node *node, t_node *new_node) {
    if (list->size == 0) {
        // list is empty
        list->head = new_node;
        list->tail = new_node;
        list->size = 1;
    } else {
        if (node == 0) {
            // put the new node at the beginning
            new_node->next = list->head;
            list->head = new_node;
            list->size++;
        } else {
            // insert the new node right after the node
            new_node->next = node->next;
            node->next = new_node;
            if (list->tail == node) {
                // we want to insert after the tail
                list->tail = new_node;
                list->size++;
            }
        }
    }
} 

void delete_node(t_list *list, t_node *dnode) {
    t_node *node_ptr;
    if (list->size == 1) {
        list->head = 0;
        list->tail = 0;
        list->size = 0;
        
    } else {
        if (list->head == dnode) {
            // we want to delete the head of our list    
            list->head = dnode->next;
            list->size--;
            
        } else {
            node_ptr = list->head;
            while(node_ptr != 0) {
                if (node_ptr->next == dnode) {
                    if(dnode == list->tail) {
                        list->tail = node_ptr; 
                    }
                node_ptr->next = dnode->next;
                list->size--;
                
                return;
                }
                node_ptr = node_ptr->next;
            }
        }    
    }
}

int main() {
    t_list list = {0,0,0};
    t_node node = {0, 20};
    insert_node(&list, 0, &node);
    printlist(&list);
    return 0;    
}