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?

Related problem: Reverse Integer

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

思路：每次得到最后一位，然后 | 到result, result <<1;

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