Grokking the Coding Interview: Patterns for Coding Questions

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 == arr.length`
- `0 <= n <= 3500`
- `-100 <= arr[i] <= 100`
- `-100 <= target <= 100`

## Try it yourself  
 Try solving this question here: