LeetCode 190. Reverse Bits

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        int ans = 0;
        for (int i = 0; i < 32 && n > 0; ++i) {
            ans |= (n & 1) << (31 - i);
            n >>= 1;
        }
        return ans;
    }
};