The very hardest PE problems are almost completely mathematical and require very straightforward code. There's a few amazing computational ones interspersed, l

The very hardest PE problems are almost completely mathematical and require very straightforward code. There's a few amazing computational ones interspersed, like the Numbermind one, but in general I didn't find that the further along I went the harder I worked out my elegant programming skills. It was mostly doing math on paper and pressing it into code.