mediumBlind 75
3Sum
Return all unique triplets that sum to zero. Each triplet sorted ascending; the list of triplets sorted ascending too. Example: [-1,0,1,2,-1,-4] => [[-1,-1,2],[-1,0,1]]
3Sum is Two Sum with a twist: sort first, then walk two pointers inward for each anchor. The real trick is skipping duplicates cleanly so your answer set stays unique. Nail that and you have a template for 4Sum and every k-sum that follows.
Arrays & HashingTwo Pointers
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13Summedium
Based onLeetCode