力扣labuladong——一刷day15

提示：文章写完后，目录可以自动生成，如何生成可参考右边的帮助文档

---

前言

---

一、力扣92. 反转链表 II

/**
 * 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 {
    ListNode post;
    public ListNode reverseBetween(ListNode head, int left, int right) {
        if(left == 1){
            return reverseN(head,right);
        }
        head.next = reverseBetween(head.next,left-1,right-1);
        return head;
    }
    public ListNode reverseN(ListNode head, int n){
        if(n == 1){
            post = head.next;
            return head;
        }
        ListNode last = reverseN(head.next,n-1);
        head.next.next = head;
        head.next = post;
        return last;
    }
}

二、力扣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) {
        if(head == null || head.next == null){
            return head;
        }
        ListNode last = reverseList(head.next);
        head.next.next = head;
        head.next = null;
        return last;
    }
}