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]]