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3Sum

Two Pointers·Medium

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.

The solution set must not contain duplicate triplets. Each triplet should be returned in non-decreasing order, and the list of triplets should also be sorted.

Examples

Input: nums = [-1,0,1,2,-1,-4]

Output: [[-1,-1,2],[-1,0,1]]

The triplets that sum to zero are [-1,-1,2] and [-1,0,1]. Note [-1,0,1] and [0,1,-1] are the same triplet.

Input: nums = [0,1,1]

Output: []

Input: nums = [0,0,0]

Output: [[0,0,0]]

Constraints

3 <= nums.length <= 3000
-10^5 <= nums[i] <= 10^5

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Tests

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Passed32 ms

First attempt — retry to track metric movement here.

Your approach

Pattern:Two Pointers
Time:O(N)
Space:O(1)

Complete approach — pattern and complexity both named.

Coach

What you got right

You correctly matched the sorted input requirement and implemented a linear-time scan using two pointers.

Where it diverged

No divergence detected. The code correctly aligns with the stated approach.

Next attempt: focus on

Try solving related sliding window problems to build familiarity with two-pointer variants.

Signals

No signals fired — clean run, you stayed in flow.