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Three Sum

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

The solution set must not contain duplicate triplets. Output each triplet sorted, one per line, with triplets sorted lexicographically.

Example:

Input:

-1,0,1,2,-1,-4

Output:

-1 -1 2
-1 0 1

Reasoning:

The input array nums is first sorted to apply the two-pointer technique: $[-4, -1, -1, 0, 1, 2]$ .
We iterate over the array and for each element, we use two pointers, one starting from the next element and one from the end, to find a pair that sums to $-nums[i]$ .
For $nums[0] = -4$ , no triplet sums to $0$ , but for $nums[1] = -1$ , we find $-1 + 0 + 1 = 0$ and for $nums[2] = -1$ , we find $-1 + -1 + 2 = 0$ .
These two unique triplets $[-1, 0, 1]$ and $[-1, -1, 2]$ are then sorted and output, resulting in the given sample output.

Constraints:

3 <= len(nums) <= 3000
-10^5 <= nums[i] <= 10^5

Editor

Python 3.13.1

Test Results

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