题解 | #链表内指定区间反转#

import java.util.*;

/**
  public class ListNode {
     int val;
     ListNode next = null;
    public ListNode(int val) {
       this.val = val;
     }
   }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param head ListNode类 
     * @param m int整型 
     * @param n int整型 
     * @return ListNode类
     */
    public ListNode reverseBetween (ListNode head, int m, int n) {
        ListNode dummy = new ListNode(-1);
        dummy.next = head;

        ListNode pre = dummy;
        ListNode curr = head;

        for(int i = 0 ; i<m-1; i++){
            pre = pre.next;
            curr = curr.next;
        }
        
        for(int i = 0; i< n-m; i++){
            ListNode temp  = curr.next;
            curr.next = temp.next;
            temp.next = pre.next;
            pre.next = temp;
        }

        return dummy.next;

    }
}