方法一:建立虚拟头结点辅助反转
创建一个虚拟头节点,获取链表中每个节点,用虚拟头节点指向这个节点,并在链表中删除,
/**
* 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 ans = new ListNode(-1);
ListNode cur = head;
while(cur != null){
ListNode next = cur.next;
cur.next = ans.next;
ans.next = cur;
cur = next;
}
return ans.next;
}
}
方法二:直接操作链表实现反转
记录当前节点(cur),前驱节点(pre),后继节点(next),先将当前节点的下一个节点指向前驱节点,然后将当前节点赋给前驱节点,后继节点赋给当前节点
文章来源:https://www.toymoban.com/news/detail-633810.html
/**
* 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 = head;
while(cur != null){
ListNode next = cur.next;
cur.next = pre;
pre = cur;
cur = next;
}
return pre;
}
}
方法三:递归文章来源地址https://www.toymoban.com/news/detail-633810.html
/**
* 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 || head.next == null) {
return head;
}
ListNode newHead = reverseList(head.next);
head.next.next = head;
head.next = null;
return newHead;
}
}
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