### Number of 1s in 2's complement representation

Source: Interview Street CodeSprint (slightly modified) Problem: One of the basics of Computer Science is knowing how numbers are represented in 2's complement. Imagine that you write down all numbers between A and B inclusive in 2's complement representation using 32 bits. How many 1's will you write down in all ? Input: Two integers A and B Output: The number of 1s Constraints: -2^31 <= A <= B <= 2^31 - 1 Find the asymptotically optimal algorithm.