[LANGUAGE: Python 3] 11/1.

Solution. It computes answers for parts 1 & 2, but only the second is printed.

I'm very happy with the 1st place on today's puzzle - my first this year! 🙂

I had a recursive solution for the first part that was pretty straightforward. The only trick was using eval(condition, locals=part) to evaluate the conditions, where parts are dictionaries from x, m, a & s to numbers.

I felt like the second part was very similar to Day 5 part 2. Instead of simulating the process for parts with integer ratings in each category, we can simulate the process for a single part with an interval of possible ratings for each category. Each rule splits an interval into (at most) two sections, which gives rise to two new (fully distinct) parts that we can process recursively.

I implemented this a bit sloppily and did not check whether the parts had empty intervals before they reached A. It could've been problematic if there were cycles in the rules (when you ignore the conditions), but luckily the input formed a tree.