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[shubha-rajan]

Hash Table Practice

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Comprehension Questions

Question	Answer
Why is a good Hash Function Important?	A good hash function makes insertion and lookup of elements as effficient as possible.
How can you judge if a hash function is good or not?	A good hash function minimizes collisions and efficiently handles collisions when they do occur
Is there a perfect hash function? If so what is it?	Perfect hash functions, or hash functions with no collisions, are only possible if the set of key values is known in advance (reference: http://courses.cs.vt.edu/~cs3114/Fall09/wmcquain/Notes/T17.PerfectHashFunctions.pdf)
Describe a strategy to handle collisions in a hash table	One strategy to handle collisions in hash tables is Separate Chaining, where values are stored in linked lists at every index. When there is a collision, the new value is appended to the linked list. Another method is open addressing, where there is both a hashing and incrementing function, and if a hash index is already full, the incrementing function is called until there is an open address to store the data. Some collision handling methods can be a combination of these two approaches.
Describe a situation where a hash table wouldn't be as useful as a binary search tree	If you need to be able to iterate through keys in a specific order, or find a min or max key.
What is one thing that is more clear to you on hash tables now	The different ways hash tables handle collisions

[CheezItMan]

Thanks for getting this in. Nice work, you hit all the learning goals here. Well done!

[CheezItMan]

👍

[CheezItMan]

Since you're building a hash of unique elements I would say that dominates the time complexity.

So O(m) where m is the number of unique elements.

[CheezItMan]

Nice, although you might be able to reduce the complexity of this loop a bit by creating a method.