Lecture 27

Learning objectives

After this class, you should be able to:

1. Derive the worst case and expected case time complexities for insertion into a hash table.
2. Given a hash function, initial hash table size, a collision resolution strategy, and a sequence of insertions and searches, show the state of the hash table after the sequence of operations, rehashing when necessary.

Reading assignment

1. Section 5.5.
2. Lecture: Hash tables.

Exercises and review questions

• Exercises and review questions on current lecture's material
  1. Show the state of a hash table without chaining having initial size 11 with f(i) = i + 3 after the following sequence of operations are complete. Use the hash function in slide 11 of Lecture 24 for the hashing. insert("abcd"), insert("dbcd"), search("decd"), insert("abdc"), insert("bbcd"), insert("dabc"), search("decd"), insert("decd"). Assume that the table size is increased when the occupancy exceeds 50%. When the size is increased, it is made the smallest prime number greater than double the current size.
  2. We discussed the need for rehashing when the hash table size is increased. Could rehashing be useful when the hash table size has not increased?

• Questions on next lecture's material
  1. None.

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Last modified: 4 Nov 2011