刷题 | leetcode 206 反转链表

给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。

示例 1：

输入：head = [1,2,3,4,5]
输出：[5,4,3,2,1]

解题思路：这种题要么递归，要么迭代，就是Python总部通过，不知道啥原因，换成Java一下就过了

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {
        ListNode pre = null;
        ListNode curr = head;
        while(curr != null){
            ListNode next = curr.next;
            curr.next = pre;
            pre = curr;
            curr = next;
        }

        return pre;
    }
}