Reverse Linked List II

题目地址：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,

return 1->4->3->2->5->NULL.

Note:
Given m, n satisfy the following condition:
1 ≤ m ≤ n ≤ length of list.

就三步：截取，旋转，拼接：

public class ReverseLinkedListII {
    public static ListNode reverseBetween(ListNode head, int m, int n) {
        if (head == null)
            return head;

        if (m == n)
            return head;

        ListNode p = head;

        ListNode q = head;
        for (int i = 1; i < n; i++)
            q = q.next;

        // Get the tail of the list
        ListNode k = null;
        if (q != null)
            k = q.next;
        // cut the tail of the list
        q.next = null;

        if (m == 1) {
            head = reverseWholeLinkedList(p);
            ListNode t = head;
            while (t.next != null) {
                t = t.next;
            }
            t.next = k;
        } else {
            for (int i = 1; i < m - 1; i++) {
                p = p.next;
            }
            ListNode t = p;
            p = p.next;
            // link the reversed list
            t.next = reverseWholeLinkedList(p);
            while (t.next != null) {
                t = t.next;
            }
            t.next = k;
        }
        return head;
    }

    public static ListNode reverseWholeLinkedList(ListNode list) {
        if (list == null)
            return list;

        if (list.next == null)
            return list;

        ListNode p = list;
        p = p.next;
        ListNode q = list;
        q.next = null;



        while (p != null) {
            ListNode k = p.next;
            p.next = q;
            q = p;
            p = k;
        }

        return q;
    }

    public static void printLinkedList(ListNode list) {
        if (list == null)
            return;

        ListNode node = list;

        while (node != null) {
            System.out.print(node.val + "->");
            node = node.next;
        }
        System.out.println("null");
    }

    public static void main(String[] args) {
        ListNode head = new ListNode(1);
        head.next = new ListNode(2);
        head.next.next = new ListNode(3);
        head.next.next.next = new ListNode(4);
        head.next.next.next.next = new ListNode(5);

        printLinkedList(reverseBetween(head, 1, 5));
    }
}