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@agesak agesak commented Apr 19, 2021

Hash Table Practice

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Comprehension Questions

Question Answer
Why is a good Hash Function Important? To avoid collisions and lookups that approach O(n) time
How can you judge if a hash function is good or not? Good hash function: 1. Fast computation 2. Uniformly distributes values 3. Hashing is random
Is there a perfect hash function? If so what is it? No
Describe a strategy to handle collisions in a hash table Linear probing, where you linearly search for the next open spot in the array to input the key/value pair
Describe a situation where a hash table wouldn't be as useful as a binary search tree When sorting matters
What is one thing that is more clear to you on hash tables now How hash functions work

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@CheezItMan CheezItMan left a comment

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Nice work Kareha, you hit the learning goals here and got the Sudoku solution as well. Well done!

Comment on lines +4 to 7
# Time Complexity: O(n) * O(mlogm)
# Space Complexity: O(n+m) = O(n)

def grouped_anagrams(strings)

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👍 We normally write the time complexity O(n + m log m)

Comment on lines +19 to 21
# Time Complexity: O(nlogn)
# Space Complexity: O(n)
def top_k_frequent_elements(list, k)

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👍

return true
end

def matrix_helper(matrix, i, j)

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I like the helper function here.

Comment on lines +46 to 48
# Time Complexity: O(n^2) - where n and n are rows and cols
# Space Complexity: O(n) - bc hash table created for every row/col separately
def valid_sudoku(table)

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👍 Nice work

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2 participants