Rotate_list.java

/*

Given the head of a linked list, rotate the list to the right by k places.

 

Example 1:


Input: head = [1,2,3,4,5], k = 2
Output: [4,5,1,2,3]
Example 2:


Input: head = [0,1,2], k = 4
Output: [2,0,1]
 

Constraints:

The number of nodes in the list is in the range [0, 500].
-100 <= Node.val <= 100
0 <= k <= 2 * 109

*/

class Rotate_List {
    public ListNode rotateRight(ListNode head, int k) {
        if (head == null) {
            return head;
        }

        ListNode last = head;
        int n = 1;

        while (last.next != null) {
            n++;
            last = last.next;
        }

        k = k % n;

        if (k == 0) {
            return head;
        }

        int count = 1;
        ListNode t = head;

        while (count < n - k) {
            t = t.next;
            count++;
        }

        ListNode res = t.next;

        
        last.next = head;

        
        t.next = null;

        return res;
    }
}