<p>Given the <code>head</code> of a linked&nbsp;list, rotate the list to the right by <code>k</code> places.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/rotate1.jpg" style="width: 450px; height: 191px;" />
<pre>
<strong>Input:</strong> head = [1,2,3,4,5], k = 2
<strong>Output:</strong> [4,5,1,2,3]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/roate2.jpg" style="width: 305px; height: 350px;" />
<pre>
<strong>Input:</strong> head = [0,1,2], k = 4
<strong>Output:</strong> [2,0,1]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the list is in the range <code>[0, 500]</code>.</li>
	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
	<li><code>0 &lt;= k &lt;= 2 * 10<sup>9</sup></code></li>
</ul>

class Solution {
public:
    ListNode* rotateRight(ListNode* head, int k) {
        // base cases
        if (head == NULL) return NULL;
        if (head->next == NULL) return head;
        // close the linked list into the ring
        ListNode* old_tail = head;
        int n;
        for (n = 1; old_tail->next != NULL; n++) old_tail = old_tail->next;
        old_tail->next = head;
        // find new tail : (n - k % n - 1)th node
        // and new head : (n - k % n)th node
        ListNode* new_tail = head;
        for (int i = 0; i < n - k % n - 1; i++) new_tail = new_tail->next;
        ListNode* new_head = new_tail->next;
        // break the ring
        new_tail->next = NULL;
        return new_head;
    }
};
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