题解 | #反转链表# | Rust

/**
 *  #[derive(PartialEq, Eq, Debug, Clone)]
 *  pub struct ListNode {
 *      pub val: i32,
 *      pub next: Option<Box<ListNode>>
 *  }
 * 
 *  impl ListNode {
 *      #[inline]
 *      fn new(val: i32) -> Self {
 *          ListNode {
 *              val: val,
 *              next: None,
 *          }
 *      }
 *  }
 */
struct Solution{

}

impl Solution {
    fn new() -> Self {
        Solution{}
    }

    /**
    * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
    *
    * 
        * @param head ListNode类 
        * @return ListNode类
    */
    pub fn ReverseList(&self, head: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
        let mut ans = ListNode{val:-1, next:None};
        let mut head = head;
        while head.is_some() {
            let head_next = head.as_mut().unwrap().next.take();
            let ans_next = ans.next.take();
            ans.next = head;
            ans.next.as_mut().unwrap().next = ans_next;
            head = head_next;
        }
        return ans.next;
    }
}