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| 1 | +<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 < j < k</code> and <code>arr[i] + arr[j] + arr[k] == target</code>.</p> |
| 2 | + |
| 3 | +<p>As the answer can be very large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p> |
| 4 | + |
| 5 | +<p> </p> |
| 6 | +<p><strong>Example 1:</strong></p> |
| 7 | + |
| 8 | +<pre><strong>Input:</strong> arr = [1,1,2,2,3,3,4,4,5,5], target = 8 |
| 9 | +<strong>Output:</strong> 20 |
| 10 | +<strong>Explanation: </strong> |
| 11 | +Enumerating by the values (arr[i], arr[j], arr[k]): |
| 12 | +(1, 2, 5) occurs 8 times; |
| 13 | +(1, 3, 4) occurs 8 times; |
| 14 | +(2, 2, 4) occurs 2 times; |
| 15 | +(2, 3, 3) occurs 2 times. |
| 16 | +</pre> |
| 17 | + |
| 18 | +<p><strong>Example 2:</strong></p> |
| 19 | + |
| 20 | +<pre><strong>Input:</strong> arr = [1,1,2,2,2,2], target = 5 |
| 21 | +<strong>Output:</strong> 12 |
| 22 | +<strong>Explanation: </strong> |
| 23 | +arr[i] = 1, arr[j] = arr[k] = 2 occurs 12 times: |
| 24 | +We choose one 1 from [1,1] in 2 ways, |
| 25 | +and two 2s from [2,2,2,2] in 6 ways. |
| 26 | +</pre> |
| 27 | + |
| 28 | +<p> </p> |
| 29 | +<p><strong>Constraints:</strong></p> |
| 30 | + |
| 31 | +<ul> |
| 32 | + <li><code>3 <= arr.length <= 3000</code></li> |
| 33 | + <li><code>0 <= arr[i] <= 100</code></li> |
| 34 | + <li><code>0 <= target <= 300</code></li> |
| 35 | +</ul> |
| 36 | +</div> |
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