mirror of
https://gitee.com/coder-xiaomo/leetcode-problemset
synced 2025-01-10 18:48:13 +08:00
46 lines
1.4 KiB
HTML
46 lines
1.4 KiB
HTML
<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>
|
|
|
|
<p>As the answer can be very large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>
|
|
|
|
<p> </p>
|
|
<p><strong class="example">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 class="example">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><strong class="example">Example 3:</strong></p>
|
|
|
|
<pre>
|
|
<strong>Input:</strong> arr = [2,1,3], target = 6
|
|
<strong>Output:</strong> 1
|
|
<strong>Explanation:</strong> (1, 2, 3) occured one time in the array so we return 1.
|
|
</pre>
|
|
|
|
<p> </p>
|
|
<p><strong>Constraints:</strong></p>
|
|
|
|
<ul>
|
|
<li><code>3 <= arr.length <= 3000</code></li>
|
|
<li><code>0 <= arr[i] <= 100</code></li>
|
|
<li><code>0 <= target <= 300</code></li>
|
|
</ul>
|