Consider a hash table with 100 slots. Collisions are resolved using chaining. Assuming simple uniform hashing, what is the probability that the first 3 slots are unfilled after the first 3 insertions?
A) (97 × 97 × 97)/100³
B) (99 × 98 × 97)/100³
C) (97 × 96 × 95)/100³
D) (97 × 96 × 95)/(3! × 100³)
Solution :
A) is correct.
Simple Uniform hashing function is a hypothetical hashing function that evenly distributes items into the slots of a hash table. Moreover, each item to be hashed has an equal probability of being placed into a slot, regardless of the other elements already placed.
Probability that the first 3 slots are unfilled after the first 3 insertions = (probability that first item doesn't go in any of the first 3 slots)*(probability that second item doesn't go in any of the first 3 slots)*(probability that third item doesn't go in any of the first 3 slots)
= (97/100) * (97/100) * (97/100)