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// @Title: 反转链表 (反转链表 LCOF)
// @Author: 15816537946@163.com
// @Date: 2022-02-02 14:07:28
// @Runtime: 0 ms
// @Memory: 2.4 MB
// 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 reverse_list(mut head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
        if head.is_none() {
            return None;
        }

        let mut prev = None;
        let mut cur = head;

        while let Some(mut v) = cur.take() {
            let next = v.next.take();
            v.next = prev.take();
            prev = Some(v);
            cur = next;
        }
        prev
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_case1() {
        let input = to_list(vec![1, 2, 3, 4, 5]);
        assert_eq!(
            Solution::reverse_list(input),
            (to_list(vec![5, 4, 3, 2, 1])),
        );
    }
}