Reverse Bits
描述
Reverse bits of a given 32 bits unsigned integer.
For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 00111001011110000010100101000000).
Follow up: If this function is called many times, how would you optimize it?
分析
最简单直接的做法，从右向左把一位位取出来，添加到新生成的整数的最低位即可。
第二个简单的方法，左右不断交换位，直到相遇。