(leetcode) 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

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        uint32_t answer = 0;
        uint32_t i = 1;
        for(i = 1; i != 0;i<<=1)// 左移32次
        {
            answer <<= 1;
            if(n & 1) answer |= 1;
            n >>= 1;
        }
        return answer;
    }
};