list! macro for ListNode on leetcode

list_node.rs

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

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

fn make_list(nodes: &[i32]) -> Option<Box<ListNode>> {
    let ns: Vec<ListNode> = nodes.iter().rev().map(|x| ListNode::new(*x)).collect();
    let mut prev_node: Option<ListNode> = None;
    for mut node in ns.into_iter() {
        if let Some(n) = prev_node {
            node.next = Some(Box::new(n));
        }
        prev_node = Some(node);
    }
    prev_node.map(Box::new)
}

macro_rules! list {
    ($($x:expr),*) => {
        make_list(&[$($x),*])
    };
}

#[test]
fn test_make_list() {
    let mut node = make_list(&[1, 2, 5]).unwrap();
    assert_eq!(1, node.val);
    node = node.next.unwrap();
    assert_eq!(2, node.val);
    node = node.next.unwrap();
    assert_eq!(5, node.val);
}

#[test]
fn test_list_macro() {
    assert_eq!(make_list(&[1, 2, 3]), list![1, 2, 3]);
}