Somewhat simplified black/white balance penalty calculation in all language versions.

cpp/QrCode.cpp

@@ -485,10 +485,11 @@ long QrCode::getPenaltyScore() const {
 				black++;
 		}
 	}
+	// Note that size is odd, so black/total != 1/2
 	int total = size * size;
-	// Find smallest k such that (45-5k)% <= dark/total <= (55+5k)%
-	for (int k = 0; black*20L < (9L-k)*total || black*20L > (11L+k)*total; k++)
-		result += PENALTY_N4;
+	// Compute the smallest integer k >= 0 such that (45-5k)% <= black/total <= (55+5k)%
+	int k = static_cast<int>((std::abs(black * 20L - total * 10L) + total - 1) / total) - 1;
+	result += k * PENALTY_N4;
 	return result;
 }