#[derive(PartialEq, Eq, Clone, Debug)]
pub struct ListNode {
    pub val: i32,
    pub next: Option<Box<ListNode>>
}

impl ListNode {
    #[inline]
    pub fn new(val: i32) -> Self {
        Self { next: None, val }
    }
}

#[macro_export]
macro_rules! list {
    () => { None };
    ( $first:expr ) => { Some(Box::new(ListNode::new($first))) };
    ( $first:expr, $($x:expr),+ ) => {
        {
            let mut head = Box::new(ListNode::new($first));
            let mut tail = &mut head;
            #[allow(unused_assignments)]
            {
                $(
                    tail.next = Some(Box::new(ListNode::new($x)));
                    tail = tail.next.as_mut().unwrap();
                )*
            }
            Some(head)
        }
    };
}