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HashMap•Pattern: Canonical Form / HashMap•Medium

Group anagrams together

Problem Intuition & Objective

Cluster strings that are anagrams of each other.

Time ComplexityO(n × k log k) — k = max string length
Optimal
Space ComplexityO(n×k)
Memory Bounds
Optimal Algorithmic Approach

HashMap with sorted-string keys.

Core Invariants & Edge Cases

  • Sort each string to form a canonical key
  • Use the sorted string as a HashMap key; group original strings under it
  • Alternative: character-count tuple as key (faster for long strings)
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