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https://leetcode.com/problems/reverse-linked-list-ii/#/description
Reverse a linked list from position m to n. Do it in-place and in one-pass.
For example: Given 1->2->3->4->5->NULL, m = 2 and n = 4,
1->2->3->4->5->NULL
return 1->4->3->2->5->NULL.
1->4->3->2->5->NULL