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).

Solution:

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        uint32_t r = 0;
        for(int i=0;i<32;i++){
            int x = n & 1;
            r = (r << 1) | x;
            n = n >> 1;
        }
        return r;
    }
};