struct LinkedListNode {
    next : Option<Box<LinkedListNode>>,
    data : i32
}
struct LinkedList {
    head : Option<Box<LinkedListNode>>
}
impl LinkedList {
    fn new() -> LinkedList {
        LinkedList {head: None}
    }
    fn insert(&mut self, new_data : i32) {
        if self.head.is_none() {
            self.head = Some(Box::new(LinkedListNode {next: None, data: new_data}));
            return;
        }
        let mut current = &mut self.head;
        while let Some(ref mut node) = *current {
            current = &mut node.next;
        }

        *current = Some(Box::new(LinkedListNode {next: None, data: new_data}));
    }
    fn print(self){
        if self.head.is_none() {
            println!("");
            return;
        }
        let mut current = & self.head;
        while let Some(ref node) = current {
            println!(" {} ", node.data);
            current = &node.next;
        }
    }
}

fn main(){
    let mut llist = LinkedList::new();
    llist.insert(2);
    llist.insert(4);
    llist.insert(6);
    llist.insert(8);
    llist.print();

}