【剑指OFFER】反转链表

【题目描述】

输入一个链表，反转链表后，输出新链表的表头。

 

【AC代码】

Reference: https://blog.nowcoder.net/n/2b3b3f502ee84080a1874f1d3ebb896e?f=comment

/*
public class ListNode {
    int val;
    ListNode next = null;

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode ReverseList(ListNode head) {
        if (head == null || head.next == null) return head;
        ListNode pre = null;
        ListNode next = null;
        while (head != null) {
            next = head.next;
            head.next = pre;
            pre = head;
            head = next;
        }
        return pre;
    }
}