How does the from_roman catch things like "IX" being equal to 9?

It would be more efficient to use elifs here rather than 3 ifs, as if an earlier if is true, later ones won't be.

Your code is a pleasure to read! The most readable solution, congrats!

I want to ask a question. What does the bitwise operator '|' do in this code?

This looks so readable! I still have much to learn. Thanks

I am new to codewars, how can I see the unit tests used when I press "Attempt" button? (not the ones in the "Sample Tests")

EDIT:
Figured it out, just need to print out the input array in the function and it will show up in the Log of failed tests.

Here is the "testUpAndDown":

capacity = 5;
input: ({3}, {2}, {0}, {2}, {}, {}, {5})
expectedResult: {0, 1, 2, 3, 6, 5, 3, 2, 0}

• you should be able to get the input by yourself
• expected: no idea since that does not match any of the fixed tests that I saw...

As you can see, your message and the information you gave are not really clear, for now... :o

actually, it does matter, but you have to considere the direction wanted by the different people too.

I solved this problem in C++, I passed all the test cases but I could not submit my code.. Does it mean TLE or something? I couldn't see any warnings about it

Thanks. I feel the word "queue" in problem description is kind of confusing, it turns out that the order doesn't matter at all...

[0,1,5,6,5,1,0,1,0]

This one is REALLY well named... "Tricky queues". As long as you do not find the expected answer, that means you do not have the correct algo.