经典链表反转

/**
 * 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) {
        if(head == null)return head;
        ListNode cur1 = null;
        ListNode cur2 = head;
        while(cur2.next != null){
             ListNode temp = cur2.next;
             cur2.next = cur1;
             cur1 = cur2;
             cur2 = temp;
        }
        cur2.next = cur1;
        return cur2;
    }
}