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) {
// write code here
if(head==null){
return head;
}
ListNode headFirst=new ListNode(-1);
headFirst.next=head;
ListNode left=head;
ListNode pre=headFirst;
for(int i=1;i<m;i++){
left=head.next;
pre=pre.next;
head=head.next;
}
ListNode right=left;
ListNode cur=left;
ListNode headB=null;
for(int j=m;j<=n;j++){
ListNode nextB=cur.next;
cur.next=headB;
headB=cur;
cur=nextB;
}
pre.next=headB;
right.next=cur;
return headFirst.next;
}
}