反转链表
给你单链表的头节点 head ，请你反转链表，并返回反转后的链表
/*** 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) {if(head == null){return null;}ListNode pre = null;ListNode cur = head;while(cur.next != null){head = head.next;cur.next = pre;pre = cur;cur = head;}cur.next = pre;return cur;}
}
双指针解法
