> And if the inputs are very large then the probability of contradiction in the first few characters even is extremely high, so all the upfront normalization is a huge waste.
This reminds me of "smart and gets things done". Your idea is to test whether people can get things done. An interview can test how smart they are. Both are important.
I've seen web developers with years of experience delivering successful projects who turned out to be terrible programmers. In this situation, it is nearly always because they're not smart enough or because they have an anti-intellectual outlook on life ("I found this on stack overflow, it works, I don't understand it in depth but it's good enough for me" or "why would I know that, I never needed it") or often both. They were ok churning out 4 month projects one after the other or maintaining some business web site for years, but when you have them working on difficult and complex problems, their abilities turn out to be lacking and the brilliant kid with much less experience turns out to be much more useful.
You're hired! :D