反转链表review

206. 反转链表
     

/*** 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) {//双指针法：先定义两个指针pre和cur分别指向null和head,一个临时指针tempListNode pre = null;ListNode cur = head;ListNode temp = null;while (cur != null) {//循环遍历//临时指针先存放cur.next,因为它等会会改变方向，避免丢失引用temp = cur.next;//改变指针指向，由指向后一个节点改为指向前一个节点cur.next = pre;//移动pre, cur向后移，继续后续的反转的过程pre = cur;cur = temp;}return pre;}
}