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day four done; always nice when you get the right answer first time both parts

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David
2025-12-04 22:02:11 -05:00
parent baf0c2bf99
commit 9f85cc318e
1 changed files with 138 additions and 0 deletions
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src/Day04.java Normal file
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package src;
import java.io.FileReader;
import java.time.Duration;
import java.time.Instant;
import java.util.List;
import java.util.Map;
import java.util.Scanner;
public class Day04 {
private static int neighbors = 0;
private static int score = 0;
private static int round = 0;
private static Map<String, Boolean> floor = new java.util.HashMap<>();
public static void main(String[] args) {
Instant start = Instant.now();
part1();
Instant middle = Instant.now();
part2();
Instant end = Instant.now();
IO.println("part 1: " + Duration.between(start, middle).toMillis() + " ms");
IO.println("part 2: " + Duration.between(middle, end).toMillis() + " ms");
}
private static void part1() {
try (Scanner scanner = new Scanner(new FileReader("resources/inputs/04/input"))) {
floor = new java.util.HashMap<>();
int rowIndex = 0;
int size = 0;
score = 0;
while (scanner.hasNextLine()) {
String[] row = scanner.nextLine().split("");
size = row.length;
for (int i = 0; i < size; i++) {
String key = "%s-%s".formatted(i, rowIndex);
if (row[i].equals("@")) {
floor.put(key, true);
} else {
floor.put(key, false);
}
}
rowIndex++;
}
floor.forEach((key, value) -> {
if (value) {
String[] coords = key.split("-");
int x = Integer.parseInt(coords[0]);
int y = Integer.parseInt(coords[1]);
neighbors = 0;
List.of(
"%s-%s".formatted(x - 1, y),
"%s-%s".formatted(x + 1, y),
"%s-%s".formatted(x, y - 1),
"%s-%s".formatted(x, y + 1),
"%s-%s".formatted(x + 1, y - 1),
"%s-%s".formatted(x - 1, y - 1),
"%s-%s".formatted(x + 1, y + 1),
"%s-%s".formatted(x - 1, y + 1)).forEach((coord) -> {
if (floor.getOrDefault(coord, false)) {
neighbors += 1;
}
});
if (neighbors < 4) {
score += 1;
}
}
});
IO.println(score);
} catch (Exception e) {
IO.println(e.getMessage());
}
}
private static void part2() {
try (Scanner scanner = new Scanner(new FileReader("resources/inputs/04/input"))) {
floor = new java.util.HashMap<>();
int rowIndex = 0;
int size = 0;
score = 0;
while (scanner.hasNextLine()) {
String[] row = scanner.nextLine().split("");
size = row.length;
for (int i = 0; i < size; i++) {
String key = "%s-%s".formatted(i, rowIndex);
if (row[i].equals("@")) {
floor.put(key, true);
} else {
floor.put(key, false);
}
}
rowIndex++;
}
while (true) {
Map<String, Boolean> newFloor = new java.util.HashMap<>(floor);
floor.forEach((key, value) -> {
if (value) {
String[] coords = key.split("-");
int x = Integer.parseInt(coords[0]);
int y = Integer.parseInt(coords[1]);
neighbors = 0;
List.of(
"%s-%s".formatted(x - 1, y),
"%s-%s".formatted(x + 1, y),
"%s-%s".formatted(x, y - 1),
"%s-%s".formatted(x, y + 1),
"%s-%s".formatted(x + 1, y - 1),
"%s-%s".formatted(x - 1, y - 1),
"%s-%s".formatted(x + 1, y + 1),
"%s-%s".formatted(x - 1, y + 1)).forEach((coord) -> {
if (floor.getOrDefault(coord, false)) {
neighbors += 1;
}
});
if (neighbors < 4) {
round += 1;
newFloor.put(key, false);
}
}
});
floor = newFloor;
if (round == 0) {
break;
} else {
score = score + round;
round = 0;
}
}
IO.println(score);
} catch (Exception e) {
IO.println(e.getMessage());
}
}
}