Amy W

[amythetester]

Hash Table Practice

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Comprehension Questions

Question	Answer
Why is a good Hash Function Important?	You get the O(1) lookup benefits.
How can you judge if a hash function is good or not?	If the keys are not grouped close together, it does not have a lot of collisions, the keys that are produced are as unique as possible.
Is there a perfect hash function? If so what is it?	Technically yes, but it's really hard to do. This would be if there are not collisions so each unique key only has one value.
Describe a strategy to handle collisions in a hash table	You can have an overflow data structure like an array or linked list or you can probe for an empty space in the table.
Describe a situation where a hash table wouldn't be as useful as a binary search tree	If the hash function is not a good one and all of the keys end up being the same, effectively creating a linked list. Cases where the data is sortable, but not hash friendly.
What is one thing that is more clear to you on hash tables now	How the hash function can work. :)

[CheezItMan]

Well done.

[CheezItMan]

Since you're sorting the strings this would be O(n * m log m) where m is the average length of a string. If you can assume the strings are small, you can drop the m term.