LeetCode - Rotate List

Rotate List

// consider case k =0 seperately
public ListNode rotateRight(ListNode head, int k) {
        if(head == null) return head;
        int size = 1;
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
            size++;
        }
        k  = k % size;
        if(k == 0) return head;  // when k=0 return head directly
        ListNode dummyNode = new ListNode(0);
        dummyNode.next = head;
        ListNode runner = dummyNode;
        ListNode walker = dummyNode;
        int i = 0;
        while(i < k){
            runner = runner.next;
            i++;
        }
        while(runner.next != null){
            runner = runner.next;
            walker = walker.next;
        }
        ListNode newHead = walker.next;
        runner.next = dummyNode.next;
        dummyNode.next = newHead;
        walker.next = null;
        return newHead;
    }
    
// include case: k=0 generally
 public ListNode rotateRight(ListNode head, int k) {
        if(head == null) return head;
        int size = 1;
        ListNode cur = head;
        while(cur.next != null){
            cur = cur.next;
            size++;
        }
        k  = k % size;
        // if(k == 0) return head;
        ListNode runner = head;
        ListNode walker = head;
        int i = 0;
        while(i < k){
            runner = runner.next;
            i++;
        }
        while(runner.next != null){
            runner = runner.next;
            walker = walker.next;
        }
        runner.next = head;
        ListNode newHead = walker.next;
        walker.next = null;
        return newHead;
    }