Unfortunately it seems this is all about the data structure that you use as opposed to an actual solution. Native scala collection types such as ListBuffer timed out for me, however if you use an Array as you would in Java it works, granted you have the correct logic. Disappointing.

I have been trying to solve this for ages in Scala with a O(n) solution, but keep getting execution timeout errors. Any suggestions?

for Scala , test cases have 9 digit arrays, directly conflicting instructions stating all arrays would have a length of 10 . Alters solution .