【LeetCode】Rotate List

Rotate List 
Total Accepted: 6485 Total Submissions: 30150 My Submissions
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.
题目大意是将链表右移k个单位，k为非负数。
右移链表，考察的是对链表操作的熟悉度。
注意考虑
1、链表有可能为空；
2、n == 0情况，n >= len情况；
基本思路是，先获取链表前半部分，也就是(len - n)，这个在转换之后变为新链表的后半部分。然后处理剩下的链表，这部分会变为新链表的头部。

Java AC

/**
 * 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) {
        if(n == 0 || head == null){
            return head;
        }
        int len = 0;
        ListNode p = head;
        while(p != null){
            p = p.next;
            len++;
        }
        n %= len;
        if(n == len){
            return head;
        }
        p = head;
        ListNode node1 = new ListNode(0);
        ListNode q = node1;
        int k = 0;
        while(k < (len-n)){
            q.next = new ListNode(p.val);
            q = q.next;
            p = p.next;
            k++;
        }
        ListNode node2 = new ListNode(0);
        q = node2;
        while(p != null){
            q.next = new ListNode(p.val);
            q = q.next;
            p = p.next;
        }
        q.next = node1.next;
        return node2.next;
    }
}