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3Sum is a medium coding interview question covering arrays, sorting, two pointers — the kind asked at FAANG (Facebook/Meta, Apple, Amazon, Netflix, Google) and AI-first companies like Anthropic, OpenAI, and Nvidia.
Given an integer array nums, return all unique triplets [nums[i], nums[j], nums[k]] such that i, j, k are distinct and nums[i]+nums[j]+nums[k]=0.
Example: [-1,0,1,2,-1,-4] -> [[-1,-1,2],[-1,0,1]]
No duplicate triplets in the output. Order within triplets and across triplets does not matter.
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