题解 | #链表内指定区间反转#

//采用双指针，循环遍历
import java.util.*;

/*

• public class ListNode {

• int val;

• ListNode next = null;

• } */

  public class Solution {
  
   public ListNode reverseBetween (ListNode head, int m, int n) {
   // write code here
       
  if (head == null) {
       return null;
   }
   
   int len = n - m;
   
   ListNode  right = head;
   
   for (int i = 0; i < len; i++) {
   
       right = right.next;
   }
   
   ListNode pre = new ListNode(-1);
   
   pre.next = head;
   
   ListNode preLeft = pre;
   
  
   for (int i = 1; i < m; i++) {
   
       preLeft = preLeft.next;
       
       right = right.next;
       
   }
   
   ListNode left = preLeft.next;
   
   ListNode aftLeft = left.next;
   
   preLeft.next = right;
   
   left.next = right.next;
   
  
  
       while (left != right ) {
   
       preLeft = left;
       
       left = aftLeft;
       
       aftLeft = left.next;
       
       left.next = preLeft ;
   }
   
   return   pre.next;
   
  

  }

}