CODE 41. Reverse Linked List II

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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,
return 1->4->3->2->5->NULL.
Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤ length of list.

public ListNode reverseBetween(ListNode head, int m, int n) {
	// IMPORTANT: Please reset any member data you declared, as
	// the same Solution instance will be reused for each test case.
	ListNode tmpHead = head;
	Stack<Integer> stack = new Stack<Integer>();
	int number = 1;
	if (tmpHead != null) {
		while (tmpHead != null && number < m) {
			tmpHead = tmpHead.next;
			number++;
		}
		ListNode tmp = tmpHead;
		while (tmp != null && number <= n) {
			stack.push(tmp.val);
			tmp = tmp.next;
			number++;
		}
		if (number > n) {
			while (!stack.isEmpty()) {
				tmpHead.val = stack.pop();
				tmpHead = tmpHead.next;
			}
		}
	}
	return head;
}