1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

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

#[macro_export]
macro_rules! list {
    () => {
        None
    };
    ($e:expr) => {
        ListLink::link($e, None)
    };
    ($e:expr, $($tail:tt)*) => {
        ListLink::link($e, list!($($tail)*))
    };
}

pub type ListLink = Option<Box<ListNode>>;

pub trait ListMaker {
    fn link(val: i32, next: ListLink) -> ListLink {
        Some(Box::new(ListNode { val, next }))
    }
}

impl ListMaker for ListLink {}