题解 | #链表内指定区间反转# [P2]

找到第一个要反转的数之前的数 设置为pre. 然后正常反转 (n-m-1)次
https://blog.nowcoder.net/n/82d1e33b25c84859b6442702d266e817

import java.util.*;

public class Solution {

    public ListNode reverseBetween (ListNode head, int m, int n) {
      ListNode dummyNode = new ListNode(-1);
      dummyNode.next = head;
      ListNode pre = dummyNode;
      for(int i=0;i<m-1;i++){
        pre = pre.next;
      }
      
      ListNode cur = pre.next;
      for(int i=0; i<n-m; i++){
        ListNode tmp = cur.next;
        cur.next = tmp.next;
        tmp.next = pre.next;
        pre.next = tmp;
      }
      return dummyNode.next;
    }
}