190. Reverse Bits (Int; Bit)

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?

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        uint32_t ret = 0; //NOTE: integer got from this way should be decalred as unsigned
        int tmp;
        /*把一个unsigned int 数字1一直左移，直到它变成全0的时候，也就得到了该机器内unsigned int的长度*/
        for (i = 1; i != 0; i <<= 1)
            tmp = n & 0x1;
            n >>= 1;
            ret <<= 1; //must before the operation |
            ret |= tmp;
        }
        return ret;
    }
};