题解 | #反转链表#

class ListNode {
    int val;
    ListNode next = null;

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