Richa, In your algoritm's second iteration, you can't flip cell 15..beacuse, cell 14 is not 1 by that time..it has already been flipped back to 0... The same holds for all your later iterations.. You might have generalized the result from the first iteration..but, its not so...because, the 1st iteration is special, as the 1st cell can be fliped at any time...
Vikram
