Two Sum

Arrays & Hashing is a repeated product-company interview pattern because it tests whether you can turn a brute-force idea into a predictable invariant.

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Question

Given an integer array and a target, return the two indices whose values add up to the target.

nums = [2, 7, 11, 15], target = 9 -> [0, 1]

nums = [3, 2, 4], target = 6 -> [1, 2]

Approach

Try framing your own approach first. The 30 seconds you think before peeking is where learning happens.

Clean Solution

Reveal the approach first.

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Common Mistakes

Do not sort if the question asks for original indices.
Check complement before insert to avoid reusing one element.

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