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 }