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?

Related problem: 

Credits:

Special thanks to  for adding this problem and creating all test cases.

 

https://discuss.leetcode.com/topic/42572/sharing-my-2ms-java-solution-with-explanation

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 <<= 1;            if((n & 1) == 1) res ++;            n >>=1;        }        return res;    }}