LinkedList----- List 61. Rotate List

题目连接

这道题通过率略低，，不知道为什么，有好几种的做法，几乎没什么难度，不过要是能在O（1）空间内就行了。

 public ListNode rotateRight(ListNode head, int k) {        if (head == null) {            return head;        }        ListNode p = head;        int len = computeLength(p);        int step = k % len;        if (step == 0) {            return head;        }        int pre = len - step;        p = head;        ListNode q = combinateList(p);        ListNode result = help(q, pre, len);        return result;    }    public int computeLength(ListNode head) {        ListNode p = head;        int counter = 0;        while (p != null) {            counter++;            p = p.next;        }        return counter;    }    public ListNode combinateList(ListNode head) {        ListNode p = head;        ListNode list1 = head;        ListNode list2 = null;        ListNode q = null;        while (p.next != null) {            ListNode node = new ListNode(p.val);            if (list2 == null) {                list2 = node;                q = list2;            } else {                q.next = node;                q = q.next;            }            p = p.next;        }        q.next = new ListNode(p.val);        q.next.next = null;        p.next = list2;        System.out.println("合并后：");        printListNode(list1);        return list1;    }    public ListNode help(ListNode head, int pre, int len) {        ListNode q = head;        ListNode result = null;        ListNode p = null;        int counter = 0;        int inCounter = 0;        while (q != null) {            q = q.next;            if (result == null) {                counter++;                if (counter == pre) {                    result = new ListNode(q.val);                    p = result;                    inCounter++;                }            } else {                inCounter++;                p.next = new ListNode(q.val);                p = p.next;                if (inCounter == len) {                    q = null;                    p = null;                }            }        }        return result;    }    public void printListNode(ListNode head) {        ListNode p = head;        while (p != null) {            System.out.print(p.val + "->");            p = p.next;        }        System.out.print("NULL");    }