<h2><a href="https://leetcode.com/problems/3sum-with-multiplicity/">923. 3Sum With Multiplicity</a></h2><h3>Medium</h3><hr><div><p>Given an integer array <code>arr</code>, and an integer <code>target</code>, return the number of tuples <code>i, j, k</code> such that <code>i &lt; j &lt; k</code> and <code>arr[i] + arr[j] + arr[k] == target</code>.</p>

<p>As the answer can be very large, return it <strong>modulo</strong> <code>10⁹ + 7</code>.</p>

<p>&nbsp;</p>

<p><strong>Example 1:</strong></p>

<pre><strong>Input:</strong> arr = [1,1,2,2,3,3,4,4,5,5], target = 8

<strong>Output:</strong> 20

<strong>Explanation: </strong>

Enumerating by the values (arr[i], arr[j], arr[k]):

(1, 2, 5) occurs 8 times;

(1, 3, 4) occurs 8 times;

(2, 2, 4) occurs 2 times;

(2, 3, 3) occurs 2 times.

</pre>

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

<pre><strong>Input:</strong> arr = [1,1,2,2,2,2], target = 5

<strong>Output:</strong> 12

<strong>Explanation: </strong>

arr[i] = 1, arr[j] = arr[k] = 2 occurs 12 times:

We choose one 1 from [1,1] in 2 ways,

and two 2s from [2,2,2,2] in 6 ways.

</pre>

<p>&nbsp;</p>

<p><strong>Constraints:</strong></p>

<ul>

<li><code>3 &lt;= arr.length &lt;= 3000</code></li>

<li><code>0 &lt;= arr[i] &lt;= 100</code></li>

<li><code>0 &lt;= target &lt;= 300</code></li>

</ul>

</div>