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Space - Nora #25

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@thenora thenora commented Sep 20, 2020

Hash Table Practice

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Comprehension Questions

Question Answer
Why is a good Hash Function Important? hash functions can solve a lot of problems with a pretty efficient big O
How can you judge if a hash function is good or not? too many collisions in a hash function isn't very efficient
Is there a perfect hash function? If so what is it? no?
Describe a strategy to handle collisions in a hash table Chaining lets you link a list of records that have same hash function value
Describe a situation where a hash table wouldn't be as useful as a binary search tree for sorted data
What is one thing that is more clear to you on hash tables now various ways to handle collisions

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@CheezItMan CheezItMan left a comment

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Nice work Nora, you hit the learning goals here. Check out my small comments on time complexity. Well done.

Comment on lines +4 to 7
# Time Complexity: O(n^2) or O(m * n) where m is the number of words and n is the characters
# Space Complexity: O(n) where n is the number of words in the array

def grouped_anagrams(strings)

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You are right that it's O(nm) which isn't O(n^2) unless n and m are the same. On the other hand if the words are all relatively small (like English words, you can call this O(n).

Comment on lines +25 to 28
# in the case of a tie it will select the first occurring element.
# Time Complexity: O (n log n) due to sort_by / quick sort - best case. Worst case is O(n^2) if the data is already ordered
# Space Complexity: O(n)
def top_k_frequent_elements(list, k)

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👍 , although since Ruby uses MergeSort, this is always O(n log n)

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