题目：

题解：

class Solution {public ListNode reverseBetween(ListNode head, int left, int right) {// 设置 dummyNode 是这一类问题的一般做法ListNode dummyNode = new ListNode(-1);dummyNode.next = head;ListNode pre = dummyNode;for (int i = 0; i < left - 1; i++) {pre = pre.next;}ListNode cur = pre.next;ListNode next;for (int i = 0; i < right - left; i++) {next = cur.next;cur.next = next.next;next.next = pre.next;pre.next = next;}return dummyNode.next;}
}