190. Reverse Bits

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?

Solution:

The idea is very straightforward, get rightmost bit by calculating n& 1 append to the result r. Shift n to the right each time to discard the processed digit. 

 public int reverseBits(int n) {  
    int r=0;  
     for(int i=0;i<32;i++){  
       r=((r<<1) | (n & 1));  
       n=n>>>1;  
     }  
     return r;  
   }