According to https://wiki.python.org/moin/TimeComplexity, x in s operation take O(n) in worst case.
Since set use hash internally, I think it should be O(1) instead of O(n)?
According to https://wiki.python.org/moin/TimeComplexity, x in s operation take O(n) in worst case.
Since set use hash internally, I think it should be O(1) instead of O(n)?