Day 6 implementation in Java

java/src/main/java/day6/Main.java

@@ -0,0 +1,49 @@
+package day6;
+
+import io.vavr.collection.List;
+import util.FileReader;
+
+
+public class Main {
+    private static final boolean ARE_SPACES_IGNORED = true;
+    private static final String TIMES_LINE_PREFIX = "Time:";
+    private static final String DISTANCES_LINE_PREFIX = "Distance:";
+
+    public static void main(String[] args) {
+        String inputFilePath = System.getProperty("user.dir") + "\\java\\src\\main\\java\\day6\\input.txt";
+        FileReader reader = new FileReader(inputFilePath);
+        List<String> inputData = List.ofAll(reader.readContents());
+
+        if (ARE_SPACES_IGNORED) {
+            inputData = inputData.map(string -> string.replaceAll(" ", ""));
+        }
+
+        List<Long> times = List.of(inputData.get(0)
+                .replace(TIMES_LINE_PREFIX, "")
+                .split(" "))
+            .filter(string -> !string.isEmpty())
+            .map(Long::parseLong);
+        List<Long> distances = List.of(inputData.get(1)
+                .replace(DISTANCES_LINE_PREFIX, "")
+                .split(" "))
+            .filter(string -> !string.isEmpty())
+            .map(Long::parseLong);
+
+        Long multipliedValues = times.zip(distances)
+            .map(timeAndDistance -> getValidHoldingTimesCount(timeAndDistance._1, timeAndDistance._2))
+            .foldLeft(1L, (accumulator, value) -> accumulator * value);
+        System.out.println(multipliedValues);
+    }
+
+    /**
+     * Solves the equation (raceTime - holdingTime) * holdingTime > recordDistance
+     */
+    private static Long getValidHoldingTimesCount(Long raceTime, Long recordDistance) {
+        Double discriminant = Math.sqrt(raceTime * raceTime - 4 * recordDistance);
+
+        Long maximumHoldingTime = (long) Math.floor((raceTime + discriminant) / 2.);
+        Long minimumHoldingTime = (long) Math.ceil((raceTime - discriminant) / 2.);
+
+        return maximumHoldingTime - minimumHoldingTime + 1;
+    }
+}