For Time limit exceeded:
If you get time limit exceeded, it must mean that you're trying to modify the
input string (i.e. trying to delete i-th chars). Try creating a new OUTPUT string
without modifying the INPUT string.

Note: if you're using a high language such as java or C#, try using the StringBuilder
object to build your output string.

For Wrong Answer(WA):
If you get WA, try some of these test cases:

Input: "dddd"
Output: ""

Input: "ddddd"
Output: "d"

Input: "abba"
Output: ""

Input: "abbbbac"
Output: "c"

Input: "wliisddsmmleeddw"
Output: ""

Input: "avcbbffcv"
Output: "a"

Hope this helps.

Edited by author 12.07.2012 00:47

Спасибо, помогло!

Thanks a lot...I could'n understand the problem statement first, now, reading ur comment I clearly understood the problem.

for me problem was that program was returning "axx" on "aaaxx"

Edited by author 18.03.2017 19:56

thanks!

Thanks