题目：

题解：

func reverseBetween(head *ListNode, left, right int) *ListNode {// 设置 dummyNode 是这一类问题的一般做法dummyNode := &ListNode{Val: -1}dummyNode.Next = headpre := dummyNodefor i := 0; i < left-1; i++ {pre = pre.Next}cur := pre.Nextfor i := 0; i < right-left; i++ {next := cur.Nextcur.Next = next.Nextnext.Next = pre.Nextpre.Next = next}return dummyNode.Next
}