So do you get any actual useful information out of codewars - you know, more than "it doesn't work"?
Also, I'm guessing "abc#d##c" isn't the actual (or only) string being tested.
You need to take care of all the pathological cases such as "#####" and "ab###cd" that would underflow the string if treated naively.
Not that it hasn't happened before.
FGA: The CSRSS Backspace Bug in Windows NT 4/NT 2000/NT XP
