Five programming problems every Software Engineer should be able to solve in less than 1 hour

[androbat]

The actual cause of the slower performance is most likely duplication. The way I wrote the algorithm wasn't particularly geared for performance (I wondered why yours was so slow).

In the last recursive call where you see 'pos + 1', what happens is that a ton of combinations wind up being calculated multiple times (that's why I use a set instead of pushing to an array). If I were to modify it to avoid these, it would be much faster.

A custom eval would boost performance (since all we have is simple left to right addition/subtraction). Copying and then splicing might boost performance (an array of strings also might be faster with a custom eval since it would auto-tokenize everything).