Hash tables, hash maps, and hash-based problem solving.
- Hash table/map implementation
- Hash functions
- Collision resolution
- Two-sum pattern
- Frequency counting
- Subarray sum problems
- Anagram detection
- Hash set for O(1) lookup
- Use unordered_map for O(1) average lookups
- Think of hashing for "have I seen this before?" problems
- Frequency maps solve many counting problems
- Cumulative sum + hash map for subarray problems
- Watch out for hash collisions in worst case