将一个节点数为size链表m位置到n位置之间的区间反转要求时间复杂度为On空间复杂度为O1java实现例如12345 m=2n=4 返回14325

public ListNode reverseBetween(ListNode head, int m, int n) {
    if (head == null || head.next == null || m == n) {
        return head;
    }
    ListNode dummy = new ListNode(0);
    dummy.next = head;
    ListNode prev = dummy;
    for (int i = 1; i < m; i++) {
        prev = prev.next;
    }
    ListNode curr = prev.next;
    for (int i = m; i < n; i++) {
        ListNode next = curr.next;
        curr.next = next.next;
        next.next = prev.next;
        prev.next = next;
    }
    return dummy.next;
}