/*
 * @lc app=leetcode.cn id=206 lang=golang
 *
 * [206] 反转链表
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseList(head *ListNode) *ListNode {
	if head == nil || head.Next == nil {
		return head
	}
	next := head.Next
	head.Next = nil
	res := reverseList(next)
	next.Next = head
	return res
}

// @lc code=end

// @lc code=start
/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseList(head *ListNode) *ListNode {
	var pre *ListNode
	for head != nil {
		next := head.Next
		head.Next = pre
		pre = head
		head = next
	}
	return pre
}

// @lc code=end