Would be hard to read skimming through but very neat.

rowcased, that's great that you overcame it. I tried a lot of different iterable solutions because I assumed there was one that was more optimized and that is what I was missing. I know more of what O(1) implies now. I guess college level calculus is basic math?

You seem fairly outraged over a trivial comment, you should probably take a breather. This is a place of learning and discussing, not toxicity.

A regex that is actually readable without a chart.

Code challenges are a test, on a test you can't google anything. Additionally, on a math test they tend to give you formulas for things you will encounter. In this case if the formula is provided you are still testing their ability to make it work with the limits placed, and removing the requirement to memorize formulas as I'm sure even senior programmers don't have all math formulas memorized.

This is not a 6kyu problem with the optimization requirements being imposed.

Please specify in the Details section that you are forced to be O(1) and that loop based solutions will not work.

I would classify different character capitalization as on either end to nullify being a palindrome, but I guess that depends how strict you want to be with it.

Question needs to be explained a little better for what the input is specifically because it sounds like you have two boxes and two suitcases but the tests don't support that theory.

This feels a lot like math homework and not so much programming.

Check spelling of your function versus what it is being tested against.

I think this is an excellent way to teach ternary operators. I've used them quite a bit but never like this, and I feel like I understand it better now.