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#hash-table · All writing
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Two Sum: from O(n²) brute force to a single hash-map pass
Two Sum is the first problem most people solve, and it's quietly a sales pitch for the hash map. Here's the brute force, the one trick that kills the nested loop, and the one-pass version I'd actually write.Jun 13, 2026 · 5 min read · #00001
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