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 as00111001011110000010100101000000).

Follow up:
If this function is called many times, how would you optimize it?

 

 1 public class Solution {

 2     // you need treat n as an unsigned value

 3     public int reverseBits(int n) {

 4         for(int i = 0; i < 16; i ++){

 5             int j = 31 - i;

 6             if(((n >> i) & 1) != ((n >> j) & 1)){

 7                 n ^= (1 << i) | (1 << j);

 8             }

 9         }

10         return n;

11     }

12 }

 

Swap two bit in the Integer:

1 public int swapBits(int val, int i, int j){

2     if(((val >> i) & 1) != ((val >> j) & 1)){

3         val ^= (1 << i) | (1 << j);

4     }

5     return val;

6 }