[LeetCode 061] Rotate List

Question

• 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.

Code

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null) {
            return head;
        }
        ListNode anchor = new ListNode(0);
        anchor.next = head;
        int nodeNumber = getNodeNumber(head);
        int step = k % nodeNumber;
        ListNode first = head;
        ListNode second = head;
        while (step > 0) {
            second = second.next;
            step--;
        }

        while (second.next != null) {
            first = first.next;
            second = second.next;
        }
        second.next = head;
        anchor.next = first.next;
        first.next = null;
        return anchor.next;
    }
    // calculate the number of node in the linked list
    private int getNodeNumber(ListNode head) {
        int count = 0;
        while (head != null) {
            count++;
            head = head.next;
        }
        return count;
    }
}