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));    }}