great solution

This is so effective, instead of double looping to create 2 lists...

You and I both. So much to learn. I love coming and seeing what the other's solutions are, it's almost like having hundreds of mentors seeing the different thought processes.

I forget how simple slices are, they can do so much yet I forget how great they are all the time.

this makes me feel funny

actually, #digit and #sum are two different methods, chained together. one of the beautiful things about Ruby!

i never knew of this #digit method, this is awesome!

Если честно, я совсем ничего не понял. Ну, да ладно может со временем разберусь.

Didn't get what this &-operator was doing. Can someone explain this to me?
upd Got it

very clever!

Very clean. I should have thought of this.

This means exactly: "When multiple hashtag occurrences are found, delete only the first." ;)