You might find this article on the Python wiki useful:

https://wiki.python.org/moin/TimeComplexity

1. I think, it doesn't matter because you use a dictionary like a set and both structure use hashtable or something similar under the hood.
2. It's a worst case complexity.
3. Yes, both solutions need O(n^2) time in worst case.

Hi! I am still new to this so be gentle xD
@Blind4Basics I was just looking over your solution and was wondering about it. Is that O(n)? because in worst senerio does 'if something in dict' not have O(n) complexity? In that case that solution too would be O(n^2) would it not?
It is no doubt faster than the most upvoted, but i think the complexity is the same even though yours is more like : O((n^2 + n)/2) which just translate to O(n^2).
I might be wrong and i would love it if you could explain where my knowlegde is flawed, because it 95 % of the time is xD.

Thank you!

<3

Omg never thought of that! You just made this solution so much better, that means we will only iterate through this once!

I might have misunderstood, but if you run this: litres(12.8) it returns 6 right?
That is the right answer though: 12.8 * 0.5 = 6.4. even if we took 13.8 and we would still round down to six because the assignment tells us to round down always