Reverse Bits

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?

Related problem: Reverse Integer

------------------- thinking ---------------------------------------
https://oj.leetcode.com/discuss/27405/o-1-bit-operation-c-solution-8ms
https://oj.leetcode.com/discuss/27375/my-c-10ms-version
----------------- codes------------------------------------------
class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        //int sign_bit = 0;
        //if (n < 0) {
        //    sign_bit = 1;
        //    n  = -n;
        //}
        uint32_t out = 0;
        int cnt = 32;
        while (cnt > 0) {
            int bit = n % 2;
            n = n >> 1;
            out = (out << 1) + bit;
            cnt--;
        }
        //return out + sign_bit;
        return out;
    }
};