[leetcode] Reverse Bits

From : https://leetcode.com/problems/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

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        uint32_t s, cur = 1<<31;
        while(n) {
            s += (n&1)*cur;
            cur = cur>>1;
            n = n>>1;
        }
        return s;
    }
};

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        n = ((0xAAAAAAAA&n)>>1)|((0x55555555&n)<<1);
        n = ((0xCCCCCCCC&n)>>2)|((0x33333333&n)<<2);
        n = ((0xF0F0F0F0&n)>>4)|((0x0F0F0F0F&n)<<4);
        n = ((0xFF00FF00&n)>>8)|((0x00FF00FF&n)<<8);
        n = ((0xFFFF0000&n)>>16)|((0x0000FFFF&n)<<16);
        return n;
    }
};