Hashmap Frequency / State Counting

The Hashmap Frequency / State Counting technique is applied when tackling problems characterized by specific invariants in the problem state or constraints:

• Core Strategy: Track counts or per-key state (character tallies, bijective mappings) in a single pass with a hashmap, then compare or query those counts.
• 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.