Applying rank 8 => incProgress(rank = 8),
"After applying rank of 8 expected:<0> but was:<1>" is about progress being 1, not rank

I have this problem too

Indeed. Right now I am stuck at that very place. My algo works, just times out at the big one. I guess I'm at linear efficiency and need to get to log...

I had the same issue, it wants progress to be 0, not the rank.

But the directions say n being the length of the string array, if n = 0 return "", so because the list is empty, you should return an empty string, right?

Also, notice that almost 400 coders have solved it in Dart so far.

Anyway, I don't know Dart, so not sure what else to check.

Althought if you're talking about the 3rd sample test, I was able to pass that one.

thx!