permutation, mapping, zipping and filtering are all completely idiomatic scala. There is next to no cognitive load in this 4-line solution. Brute-force attack

permutation, mapping, zipping and filtering are all completely idiomatic scala. There is next to no cognitive load in this 4-line solution. Brute-force attack on every permutation. I would say that anyone find there to be an excessive cognitive load would be someone that is not familiar with scala nor functional programming.