Source: Asked to me by Dinesh Dharme (CSE IITB Fifth year student)
You have a array of 0's and 1's. e.g. 0001011101001010100101010101100111
Find the maximum contiguous subsequence of the above sequence so the number of 0's and 1's in that subsequence are equal
Update (21 Dec 2010):
Solution: Posted by Nikhil Garg (Third year student, CSE IIT Delhi) in comments!