Swift set contains complexity

Question

Set has contains function which returns true if member exists in the set; otherwise, false.

and its complexity is O(1).

I want to know how its complexity is constant O(1) i.e. it does not depends on size

Here are the docs : https://developer.apple.com/documentation/swift/set/1540013-contains

Answer 1

It will use hash function to insert, search. Good hash function will lead to 0(1) time complexity. https://en.wikipedia.org/wiki/Hash_table