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leetcode/problem/binary-trees-with-factors.html

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+<p>Given an array of unique integers, <code>arr</code>, where each integer <code>arr[i]</code> is strictly greater than <code>1</code>.</p>
+
+<p>We make a binary tree using these integers, and each number may be used for any number of times. Each non-leaf node&#39;s value should be equal to the product of the values of its children.</p>
+
+<p>Return <em>the number of binary trees we can make</em>. The answer may be too large so return the answer <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong>Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [2,4]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> We can make these trees: <code>[2], [4], [4, 2, 2]</code></pre>
+
+<p><strong>Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> arr = [2,4,5,10]
+<strong>Output:</strong> 7
+<strong>Explanation:</strong> We can make these trees: <code>[2], [4], [5], [10], [4, 2, 2], [10, 2, 5], [10, 5, 2]</code>.</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= arr.length &lt;= 1000</code></li>
+	<li><code>2 &lt;= arr[i] &lt;= 10<sup>9</sup></code></li>
+	<li>All the values of <code>arr</code> are <strong>unique</strong>.</li>
+</ul>