61. Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

Example:

Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL. 

class Solution {

    public ListNode rotateRight(ListNode head, int k) {

        if (head == null || head.next == null) 

            return head;

        ListNode dummy=new ListNode(0);

        dummy.next = head;

        ListNode fast = dummy;

        ListNode slow = dummy;

        

        int i;

        for (i = 0; fast.next != null; i++)//让fast指向最后节点，i变成节点个数，此例子中i为5

            fast = fast.next; 

        

        for (int j = i - k % i; j > 0; j--)//j等于3，slow往前移动3次，移到3

            slow = slow.next;

        

        fast.next = dummy.next; //使得5指向1

        dummy.next = slow.next; //0指向4

        slow.next = null; //3指向null

        

        return dummy.next;        

    }

}