Algorithms & Data Structures
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Hash Maps and Sets
Trade space for speed: turn O(n) and O(n^2) scans into O(1) lookups
30 min read
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Learn how hash maps and hash sets give near-constant-time membership, lookup, and counting, and use that power to solve classic interview problems like two-sum, Sudoku validation, matrix zeroing, longest consecutive runs, and geometric-sequence counting.