190. 颠倒二进制位

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