题解 | #反转链表#

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

    ListNode(int val) {
        this.val = val;
    }
}*/
public class Solution {
    public ListNode ReverseList(ListNode head) {
        ListNode pre = null;
        ListNode cur = head; 
        ListNode tail=null; 
        while(cur!=null){
           pre= cur.next;//pre一直在cur前方
           cur.next=tail;//修改箭头
           //更新
           tail=cur;
           cur=pre;
             
        }
        return tail;
    }
}