Java: 3 Sum

Difficulty Level: MEDIUM

Problem Statement:

Given an array `nums` of n integers, are there elements a, b, c in `nums` such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Input:

nums = [-1,0,1,2,-1,-4]

Output:

[[-1,-1,2],[-1,0,1]]
The sum of -1, -1 and 2 is 0. The Sum of -1, 0,  and 1 is also 0.