Rotate List

Description

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

Example 1:

Input: 1->2->3->4->5->NULL, k = 2

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

Explanation:

rotate 1 steps to the right: 5->1->2->3->4->NULL

rotate 2 steps to the right: 4->5->1->2->3->NULL

Example 2:

Input: 0->1->2->NULL, k = 4

Output: 2->0->1->NULL

Explanation:

rotate 1 steps to the right: 2->0->1->NULL

rotate 2 steps to the right: 1->2->0->NULL

rotate 3 steps to the right: 0->1->2->NULL

rotate 4 steps to the right: 2->0->1->NULL

Code

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null) return  null;
        
        ListNode first = head;
        ListNode second = head;
        int size = 0;
        while(first != null) {
            size++;
            first = first.next;
        }
        
        k %= size;
        
        first = head;
        int count = 1;
        while (first != null && first.next != null) {
            if (count > k) second = second.next;
            first = first.next;
            count++;
        }
        
        first.next = head;
        
        ListNode result = second.next;
        
        second.next = null;
        
        return result;

    }
}