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Hash Maps & Sets
Use hash-based data structures for O(1) lookups to solve counting, grouping, and duplicate detection problems.
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Hash Maps & SetsBeginnerIntermediateAdvancedQuestions: 1–5
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What You'll Practice (3 techniques)
Frequency countingGrouping by keyTwo-sum pattern
Prerequisites
Arrays basics
Difficulty Levels
Beginner
Core pattern recognition, fundamental approach.
Intermediate
Pattern variations, edge cases, optimization.
Advanced
Complex combinations, merge multiple patterns.