Hash Tables

Trade a bit of memory for answers in constant time.

1. 1Hash Table BasicsTurn a key into an address and skip the search.4m
2. 2Two SumRemember what you have seen and the pair finds itself.5m
3. 3Frequency CountingOne pass, one counter per distinct value.4m
4. 4Group AnagramsGive every item a canonical key, then bucket by it.5m
5. 5When Hashing FailsO(1) is an average, not a promise.5m