Method partition

86. Partition List/src/main.rs:41–59

(mut head: Option<Box<ListNode>>, x: i32)

impl Solution {
    pub fn partition(mut head: Option<Box<ListNode>>, x: i32) -> Option<Box<ListNode>> {
        let mut h1 = ListNode::new(0);
        let mut h2 = ListNode::new(0);
        let mut p1 = &mut h1;
        let mut p2 = &mut h2;
        while head.is_some() {
            let mut node = head.unwrap();
            head = node.next.take();
            if node.val < x {
                p1.next = Some(node);
                p1 = p1.next.as_mut().unwrap();
            } else {
                p2.next = Some(node);
                p2 = p2.next.as_mut().unwrap();
            }
        }
        p1.next = h2.next;
        h1.next
    }
}

#[cfg(test)]