DSA · Two pointers · #12

3Sum

Module 15 · difficulty 3/5·⏱ 30:00starts on first keystroke

Given an integer array `nums`, return all unique triplets `[nums[i], nums[j], nums[k]]` such that i, j, k are distinct indices and nums[i] + nums[j] + nums[k] == 0. The solution set must not contain duplicate triplets. Order of triplets and of values within a triplet does not matter.

Examples

nums = [-1,0,1,2,-1,-4] → [[-1,-1,2],[-1,0,1]]
nums = [0,1,1] → [] — no triplet sums to 0
nums = [0,0,0] → [[0,0,0]]

Constraints

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

Session phases

A · Clarify

B · Approach

C · Complexity

D · Edges

E · Code

F · Tradeoff

G · Score

Phase A — Clarify

Ask questions about input bounds, types, and edge constraints.

Ask the coach clarifying questions about the problem.

When you've covered this phase, advance to the next.