题目描述：
everse bits of a given 32 bits unsigned integer.
For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as00111001011110000010100101000000).
解题思路：
移位操作。
代码如下：
public class Solution {
// you need treat n as an unsigned value
public int reverseBits(int n) {
int res = 0;
for(int i = 0; i < 32; i++){
res += n & 1;
if(i < 31)
res <<= 1;
n >>>= 1;
}
return res;
}
}