## Problem Statement

Given an array of unsorted numbers, find all unique triplets in it that add up to zero.

**Example 1**:

```
Input: [-3, 0, 1, 2, -1, 1, -2]
Output: [[-3, 1, 2], [-2, 0, 2], [-2, 1, 1], [-1, 0, 1]]
Explanation: There are four unique triplets whose sum is equal to zero. smallest sum.'

```
Input: [-5, 2, -1, -2, 3]
Output: [[-5, 2, 3], [-2, -1, 3]]
Explanation: There are two unique triplets whose sum is equal to zero.
```

**Constraints:**

- `3 <= arr.length <= 3000`
- -10<sup>5</sup> <= arr[i] <= 10<sup>5</sup>

## Try it yourself 
  Try solving this question here:

```
Input: [-5, 2, -1, -2, 3]
Output: [[-5, 2, 3], [-2, -1, 3]]
Explanation: There are two unique triplets whose sum is equal to zero.

```
Input: [-5, 2, -1, -2, 3]
Output: [[-5, 2, 3], [-2, -1, 3]]
Explanation: There are two unique triplets whose sum is equal to zero.

**Constraints:**

- `3 <= arr.length <= 3000`
- `-105 <= arr[i] <= 105`