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Triplets with Smaller Sum (medium)

## Problem Statement

Given an array **arr** of unsorted numbers and a target sum, count all triplets in it such that **arr[i] + arr[j] + arr[k] < target** where **i**, **j**, and **k** are three different indices. Write a function to return the count of such triplets.

**Example 1**:

```
Input: [-1, 0, 2, 3], target=3
Output: 2
Explanation: There are two triplets whose sum is less than the target: [-1, 0, 3], [-1, 0, 2]
```

**Example 2**:

```
Input: [-1, 4, 2, 1, 3], target=5
Output: 4
Explanation: There are four triplets whose sum is less than the target:
[-1, 1, 4], [-1, 1, 3], [-1, 1, 2], [-1, 2, 3]
```

**Constraints:**

`n == att.length`

`0 <= n <= 3500`

`-100 <= arr[i] <= 100`

`-100 <= target <= 100`

## Try it yourself

Try solving this question here:

Python3

Python3

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