<h2><a href="https://leetcode.com/problems/3sum/">15. 3Sum</a></h2><h3>Medium</h3><hr><div><p>Given an integer array nums, return all the triplets <code>[nums[i], nums[j], nums[k]]</code> such that <code>i != j</code>, <code>i != k</code>, and <code>j != k</code>, and <code>nums[i] + nums[j] + nums[k] == 0</code>.</p>

<p>Notice that the solution set must not contain duplicate triplets.</p>

<p>&nbsp;</p>

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

<pre><strong>Input:</strong> nums = [-1,0,1,2,-1,-4]

<strong>Output:</strong> [[-1,-1,2],[-1,0,1]]

<strong>Explanation:</strong>

nums[0] + nums[1] + nums[2] = (-1) + 0 + 1 = 0.

nums[1] + nums[2] + nums[4] = 0 + 1 + (-1) = 0.

nums[0] + nums[3] + nums[4] = (-1) + 2 + (-1) = 0.

The distinct triplets are [-1,0,1] and [-1,-1,2].

Notice that the order of the output and the order of the triplets does not matter.

</pre>

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

<pre><strong>Input:</strong> nums = [0,1,1]

<strong>Output:</strong> []

<strong>Explanation:</strong> The only possible triplet does not sum up to 0.

</pre>

<p><strong>Example 3:</strong></p>

<pre><strong>Input:</strong> nums = [0,0,0]

<strong>Output:</strong> [[0,0,0]]

<strong>Explanation:</strong> The only possible triplet sums up to 0.

</pre>

<p>&nbsp;</p>

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

<ul>

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

<li><code>-10⁵ &lt;= nums[i] &lt;= 10⁵</code></li>

</ul>

</div>