[loeg]

It really helps to (1) have taken an algorithms class and (2) be aware of Python libraries that implement common graph algorithms if you're going for time. At least, that was my impression 2016-2017. The later puzzles are impossible if you don't know a good enough algorithm (they're more or less designed to take impossible amounts of time to completely brute force).

I'd suggest new programmers do any they can reasonably understand and just skip ones that seem like they'll be frustrating or require a "fast" algorithm they don't know. (OTOH, many days' first star can be gotten with a brute force algorithm. It's usually the 2nd star that takes something more clever.)