Minimization of consecutive numbers

I have been trying to solve a question in which we have to minimize the length of consecutive same numbers.The string consists of 0 and 1 only in which we can change any 0 to 1 and 1 to 0.i have been focussing on the middle of consecutive same nos and transforming it in smaller form by using one transformation but still it is giving me wrong answer.Is there any effcient way of doing this.