you can get the problem statement from here.
after analysing the question a bit, we can come to the conclusion that 1’s in the bit string need odd toggles and 0’s in the bit string need even toggles. and also that we can safely strip the prefixed zero’s.
because if you try to toggle any of them you need to toggle some other-thing preceding that zero(which is also zero), so you don’t want to toggle the prefixed zero’s. based on these conclusions you can easily solve the problem..