0876-middle-of-the-linked-list.rs

impl Solution {
    pub fn middle_node(head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
        let (mut slow, mut fast) = (&head, &head);

        while fast.is_some() && fast.as_ref().unwrap().next.is_some() {
            fast = &fast.as_ref().unwrap().next.as_ref().unwrap().next;
            slow = &slow.as_ref().unwrap().next
        }

        slow.clone()
    }
}