61. Rotate List (Medium)

https://leetcode.com/problems/rotate-list/

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

Solutions

class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null || head.next == null) {
            return head;
        }

        // For convenience, create a dummy node that doesn't belong to the give ListNode.
        ListNode dummy = new ListNode(-1);
        dummy.next = head;

        ListNode endP = dummy;
        ListNode kthP = dummy;

        int len;

        // Get the total length of the list
        for (len = 0; endP.next != null; len++) {
            endP = endP.next;
        }

        // Get the (len - k%len)th node
        for (int j = len - (k % len); j > 0; j--) {
            kthP = kthP.next;
        }

        // Rotate the list
        endP.next = dummy.next;
        dummy.next = kthP.next;
        kthP.next = null;

        return dummy.next;
    }
}

Incorrect Solutions

References