Hashmap Grouping by Canonical Key

The Hashmap Grouping by Canonical Key technique is applied when tackling problems characterized by specific invariants in the problem state or constraints:

• Core Strategy: Bucket items together under a derived canonical key (e.g. sorted string) using a hashmap of lists.
• When to use: Look for opportunities where repeated re-computation can be replaced by maintaining monotonic properties, state windows, or relational pointers.
• Interview Signal: Demonstrating this pattern shows mastery of Hashing foundations, reducing worst-case algorithmic complexity.