206. 反转链表
解题过程
/**
* 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) {
ListNode pre = null;
ListNode cur = null;
while(head != null){
cur = head.next;
head.next = pre;
pre = head;
head = cur;
}
head = pre;
return pre;
}
}