Bloom filters
Want to check only existence of key (e.g. spelling dictionary, stolen credit cards, etc)
Small probability of error is OK.
Simple solution:
- Keep bit-table B
- For each K turn B(h(K)) on;
- Say K is in iff B(h(K)) is on;
- Works if there are no collisions! Must have
N = O(sqrt(M))
- Collisions generate false drops