190 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 as 00111001011110000010100101000000).

Follow up:
If this function is called many times, how would you optimize it?

Related problem: Reverse Integer

 

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        int i = 0, j = 31;
        while (i < j) {
            if (((n >> i) & 1) != ((n >> j) & 1)) {
                n ^= ((1U << i) | (1U << j));
            }
            i++, j--;
        }
        return n;
    }
};