Mystery Function

• Time : $O(log(n))$
• Space : $O(1)$

ulong mystery(ulong n){
  return n ^ (n >> 1);
}

ulong mysteryInv(ulong n){
  ulong mask = n >> 1;
  while(mask) {
    n ^= mask;
    mask >>= 1;
  }
  return n;
}

std::string nameOfMystery(){
  return "Gray code";
}