Well done! I had a somewhat similar experience twenty years ago in the informatics olympiads. I had no idea about the whole world of algorithms, complexity, etc. until a friend recommended to do the first round of our national informatics olympiad. The first round was pretty simple programming, the second round was a whole new world.
By the way "Ng" is Andrew Ng's surname, it's not NG with a capital G.
By the way "Ng" is Andrew Ng's surname, it's not NG with a capital G.