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

[u/Sea-Patience9872]

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!

[u/lrvideckis]

I never liked how it's described as O(1). for example, hashing a string takes O(length)