Three Sum - Leetcode 15 - Java

Given an array of integer write an algorithm to find 3 elements that sum to a zero. In short a+b+c = 0.

OR

Given an integer array nums, return all the triplets `[nums[i], nums[j], nums[k]]` such that `i != j`, `i != k`, and `j != k`, and `nums[i] + nums[j] + nums[k] == 0`.

Notice that the solution set must not contain duplicate triplets.

Good problems to cover before this one: