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.

題目大意：

給出一個單鏈表，和一個K值，根據K值往右旋轉，例如：

先求出鏈表的長度length，其實按着倒數第n%length個位置旋轉。

AC代碼：

public class Solution {
//     public ListNode reverseList( ListNode head ){
// 		if( head == null || head.next == null )
// 			return head;
// 		ListNode p = head;
// 		ListNode q = head;
// 		while( q != null ){
// 			ListNode temp = q.next;
// 			q.next = p;
// 			p = q;
// 			q = temp;
// 		}
// 		head.next = null;
// 		head = p;
// 		return head;
// 	}
	public ListNode rotateRight(ListNode head, int n){
		if( head == null || head.next == null || n<=0 )
			return head;
		ListNode before = head;
		ListNode after = head;
		int length = 0;
		while( before != null ){
			length++;
			before = before.next;
		}
		before = head;
//		if( n > length ) return reverseList(head);
        if( n%length == 0 ) return head;
		for( int i=0; i<(n%length); i++ ){
			after = after.next;
		}
		if( after == null ) return head;
		while( after.next != null ){
			before = before.next;
			after = after.next;
		}
		ListNode temp = before.next;
		before.next = null;
		after.next = head;
		head = temp;
		return head;
	}
}