3Sum (LeetCode #15)

Challenge Statement

• 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.
• This challenge corresponds to LeetCode #15.

Constraints

• 0 <= len(nums) <= 3000
• -105 <= nums[i] <= 105

Example 1:

Input: nums = [-1 , 0, 1, 2, -1, -4]

Output: [[-1, -1, 2], [-1, 0, 1]]

Example 2:

Input: nums = []

Output: []

Example 3:

Input: nums = [0]

Output: []

Solution

Below is my solution and some test cases. This solution has a quadratic time complexity O(n²) and a constant space complexity O(1), where n is the length of the input list.