leetcode 206. Reverse Linked List 反转链表 ---------- java

Reverse a singly linked list.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode reverseList(ListNode head) {
        
        if (head == null || head.next == null){
            return head;
        }
        ListNode next = head.next;
        head.next = null;
        while (next.next != null){
            ListNode node = next.next;
            next.next = head;
            head = next;
            next = node;
        }
        next.next = head;
        return next;
    }
}