Reverse a linked list from position m to n. Do it in one-pass.
count it. It just a code problem. It test your coding ability.
OHOHOH 1pass accept. I carefully think about the count and we need to choose the split part of the link list.
I divided it into whether m == 1 or not == 1.
when m == 1 we only need to reverse it to record the tale and head. each time I add a new one and take this one as head. In then end I connect the tale to element after the n. and return new head. This
In the same way, we link the m to the new head. And we return the old head if m != 1.