message: Update mirror-reflection.cpp
diff: class Solution {
  public:
  int mirrorReflection(int p, int q) {
  + // explanation commented in the following solution
  return (p & -p) > (q & -q) ? 2 : (p & -p) < (q & -q) ? 0 : 1;
  }
  };
  @@ -17,8 +18,8 @@ public:
  const auto lcm = p * q / gcd(p, q);
  // let a = lcm / p, b = lcm / q
  if (lcm / p % 2 == 1) {
  - if (lcm / q % 2 == 1) { // a is odd, b is odd <=> (p & -p) == (q & -q)
  - return 1;
  + if (lcm / q % 2 == 1) {
  + return 1; // a is odd, b is odd <=> (p & -p) == (q & -q)
  }
  return 2; // a is odd, b is even <=> (p & -p) > (q & -q)
  }
  