LeetCode_206.反转链表

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

C#代码

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

        ListNode now = new ListNode(head.val);
        head = head.next;

        while (head != null)
        {
            ListNode listNode = new ListNode(head.val);
            listNode.next = now;
            now = listNode;
            head = head.next;
        }

        return now;
    }
}