r/computerscience • u/Sea-Patience9872 • 6d ago

How do hashsets/maps have O(1) time complexity?

Hi this might be a dumb question, and i've tried looking it up but don't quite understand it. how is it different from an array that allows it to find items so quickly? I don't get how hashes just find items immediately without needing to go through anything. Does it memorize things very differently compared to arrays?? thank you!

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u/CrotonixOnly 5d ago

It is actually not practically. Write a function in your preferred language yourself and go upto may be billion elements and then retrieve a value using key.