Find all unique triplets summing to zero

## Problem Given an integer array `nums`, return **all unique triplets** `[nums[i], nums[j], nums[k]]` such that: - `i`, `j`, and `k` are **distinct indices** (`i != j != k`), and - `nums[i] + nums[j] + nums[k] == 0`. The returned triplets must be **unique** (i.e., no duplicate triplets in the output). Triplets can be returned in any order. ## Input - `nums`: an array of integers ## Output - A list/array of unique triplets, each triplet containing three integers whose sum is zero ## Constraints (typical interview bounds) - `0 <= nums.length <= 3000` - `-10^5 <= nums[i] <= 10^5` ## Example - Input: `nums = [-1, 0, 1, 2, -1, -4]` - Output: `[[-1, -1, 2], [-1, 0, 1]]`