LeetCode Rotate List

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

For example:
Given

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

and k =

2

,
return

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

.

使用两个指针，第一个先走k步，然后第二个开始走，知道第一个走到最后一个。

这样第二个指针正好是 len-k个，它就是新链表的最后一个元素。

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) {
*         val = x;
*         next = null;
*     }
* }
*/
public class Solution {
public ListNode rotateRight(ListNode head, int n) {
ListNode temp = head;
if(temp==null) return temp;
int len=0;
while (temp != null) {
++len;
temp = temp.next;
}
n = n % len;
ListNode fast=head;
ListNode slow = head;
for (int i = 0; i < n; i++) {
fast = fast.next;
}
while (fast.next != null) {
fast=fast.next;
slow = slow.next;
}
fast.next=head;
head = slow.next;
slow.next = null;
return head;
}
}