leetcode-problemset/leetcode/problem/x-of-a-kind-in-a-deck-of-cards.html

<p>In a deck of cards, each card has an integer written on it.</p>

<p>Return <code>true</code> if and only if you can choose <code>X &gt;= 2</code> such that it is possible to split the entire deck into 1 or more groups of cards, where:</p>

<ul>
	<li>Each group has exactly <code>X</code> cards.</li>
	<li>All the cards in each group have the same integer.</li>
</ul>

<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> deck = [1,2,3,4,4,3,2,1]
<strong>Output:</strong> true
<strong>Explanation</strong>: Possible partition [1,1],[2,2],[3,3],[4,4].
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> deck = [1,1,1,2,2,2,3,3]
<strong>Output:</strong> false
<strong>Explanation</strong>: No possible partition.
</pre>

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

<ul>
	<li><code>1 &lt;= deck.length &lt;= 10<sup>4</sup></code></li>
	<li><code>0 &lt;= deck[i] &lt; 10<sup>4</sup></code></li>
</ul>