Solution.rs

// Definition for singly-linked list.
// #[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
//     }
//   }
// }
impl Solution {
    pub fn partition(head: Option<Box<ListNode>>, x: i32) -> Option<Box<ListNode>> {
        let mut l = ListNode::new(0);
        let mut r = ListNode::new(0);
        let mut tl = &mut l;
        let mut tr = &mut r;
        let mut current = head;
        while let Some(mut node) = current {
            current = node.next.take();
            if node.val < x {
                tl.next = Some(node);
                tl = tl.next.as_mut().unwrap();
            } else {
                tr.next = Some(node);
                tr = tr.next.as_mut().unwrap();
            }
        }
        tr.next = None;
        tl.next = r.next;
        l.next
    }
}