061.Rotate List

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Solution 1: accepted 16ms

A common brute force solution 

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public ListNode rotateRight(ListNode head, int k) {
    if (head == null || k == 0) {
        return head;
    }
    ListNode dummy = head;
    ListNode tail = null;
    int length = 0;
    while (dummy != null) {
        tail = dummy;
        dummy = dummy.next;
        length++;
    }
    
    k = k % length;
    dummy = head;
    for (int i = 1; i < length - k; i++) {
        dummy = dummy.next;
    }
    
    ListNode newHead = head;
    if (dummy.next != null) {
        newHead = dummy.next;
        dummy.next = null;
        tail.next = head;
    }
    return newHead;
}