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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,136 @@ | ||
| package net.bqc.aoc.year2024; | ||
|
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| import net.bqc.aoc.Solution; | ||
| import net.bqc.aoc.utils.Array2DUtils; | ||
| import net.bqc.aoc.utils.Pos; | ||
|
|
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| import java.util.*; | ||
| import java.util.concurrent.atomic.AtomicLong; | ||
|
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| public class Day12 extends Solution { | ||
|
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| enum Direction { | ||
| NORTH(-1, 0), EAST(0, 1), SOUTH(1, 0), WEST(0, -1); | ||
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| final int dx, dy; | ||
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| Direction(int dx, int dy) { | ||
| this.dx = dx; | ||
| this.dy = dy; | ||
| } | ||
| } | ||
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| private char[][] plants; | ||
| private int[][] fences; | ||
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| @Override | ||
| public long solve(Part part, List<String> inputLines) { | ||
| super.solve(part, inputLines); | ||
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| this.plants = Array2DUtils.readAsMatrix(inputLines); | ||
| this.fences = computeIndividualPlantFence(); | ||
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| long price = 0; | ||
| for (int i = 0; i < plants.length; i++) { | ||
| for (int j = 0; j < fences[i].length; j++) { | ||
| if (fences[i][j] != 0) { | ||
| price += bfsAndComputePlantRegionPrice(new Pos(i, j)); | ||
| } | ||
| } | ||
| } | ||
| return price; | ||
| } | ||
|
|
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| private long bfsAndComputePlantRegionPrice(Pos startPos) { | ||
| List<Pos> visited = new ArrayList<>(); | ||
| Queue<Pos> queue = new LinkedList<>(); | ||
| queue.add(startPos); | ||
| visited.add(startPos); | ||
|
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| while (!queue.isEmpty()) { | ||
| Pos pos = queue.remove(); | ||
| for (Direction d : EnumSet.allOf(Direction.class)) { | ||
| int newX = pos.x + d.dx; | ||
| int newY = pos.y + d.dy; | ||
| Pos newPos = new Pos(newX, newY); | ||
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| if (newX < 0 || newX >= plants.length || newY < 0 || newY >= plants[0].length) continue; | ||
| if (plants[newX][newY] != plants[pos.x][pos.y] || visited.contains(newPos)) continue; | ||
|
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| queue.add(newPos); | ||
| visited.add(newPos); | ||
| } | ||
| } | ||
| return (isPart2() ? getSides(visited) : getPerimeter(visited)) * visited.size(); | ||
| } | ||
|
|
||
| private long getSides(List<Pos> visited) { | ||
| // the number of sizes is the number of corners of a region | ||
| visited.sort((o1, o2) -> o1.x * 10000 + o1.y - o2.x * 10000 - o2.y); // assume the input has maximum of 10000 columns | ||
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| long corners = 0; | ||
| int m = plants.length; | ||
| int n = plants[0].length; | ||
| for (Pos pos : visited) { | ||
| int x = pos.x, y = pos.y; | ||
|
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||
| // convex corners | ||
| if (fences[x][y] == 4) corners += 4; // single-slot plant 4 corners | ||
| else if (fences[x][y] == 3) corners += 2; // 2 corners | ||
| else if (fences[x][y] == 2) { | ||
| if (topFence(x, y) && rightFence(x, y) // NE | ||
| || bottomFence(x, y) && rightFence(x, y) // SE | ||
| || bottomFence(x, y) && leftFence(x, y) // SW | ||
| || topFence(x, y) && leftFence(x, y)) { // NW | ||
| corners++; | ||
| } | ||
| } | ||
|
|
||
| // concave corners | ||
| if (x - 1 >= 0 && y - 1 >= 0 && plants[x-1][y] == plants[x][y] && plants[x][y-1] == plants[x][y] && plants[x-1][y-1] != plants[x][y]) corners++; // NW | ||
| if (x - 1 >= 0 && y + 1 < n && plants[x-1][y] == plants[x][y] && plants[x][y+1] == plants[x][y] && plants[x-1][y+1] != plants[x][y]) corners++; // NE | ||
| if (x + 1 < m && y + 1 < n && plants[x+1][y] == plants[x][y] && plants[x][y+1] == plants[x][y] && plants[x+1][y+1] != plants[x][y]) corners++; // SE | ||
| if (x + 1 < m && y - 1 >= 0 && plants[x+1][y] == plants[x][y] && plants[x][y-1] == plants[x][y] && plants[x+1][y-1] != plants[x][y]) corners++; // SW | ||
| } | ||
| visited.forEach(pos -> fences[pos.x][pos.y] = 0); | ||
| return corners; | ||
| } | ||
|
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| private long getPerimeter(List<Pos> visited) { | ||
| AtomicLong perimeter = new AtomicLong(); | ||
| visited.forEach(pos -> { | ||
| perimeter.addAndGet(fences[pos.x][pos.y]); | ||
| fences[pos.x][pos.y] = 0; | ||
| }); | ||
| return perimeter.get(); | ||
| } | ||
|
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| private int[][] computeIndividualPlantFence() { | ||
| int[][] fences = new int[plants.length][plants[0].length]; | ||
| for (int i = 0; i < plants.length; i++) { | ||
| for (int j = 0; j < plants[0].length; j++) { | ||
| fences[i][j] += topFence(i, j) ? 1 : 0; | ||
| fences[i][j] += bottomFence(i, j) ? 1 : 0; | ||
| fences[i][j] += leftFence(i, j) ? 1 : 0; | ||
| fences[i][j] += rightFence(i, j) ? 1 : 0; | ||
| } | ||
| } | ||
| return fences; | ||
| } | ||
|
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| private boolean topFence(int i, int j) { | ||
| return i == 0 || plants[i - 1][j] != plants[i][j]; | ||
| } | ||
|
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| private boolean bottomFence(int i, int j) { | ||
| return i == plants.length - 1 || plants[i + 1][j] != plants[i][j]; | ||
| } | ||
|
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| private boolean leftFence(int i, int j) { | ||
| return j == 0 || plants[i][j - 1] != plants[i][j]; | ||
| } | ||
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| private boolean rightFence(int i, int j) { | ||
| return j == plants[0].length - 1 || plants[i][j + 1] != plants[i][j]; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,49 @@ | ||
| package net.bqc.aoc.year2024; | ||
|
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| import net.bqc.aoc.AbstractTest; | ||
| import net.bqc.aoc.Solution; | ||
| import org.junit.jupiter.api.BeforeAll; | ||
| import org.junit.jupiter.api.BeforeEach; | ||
| import org.junit.jupiter.params.ParameterizedTest; | ||
| import org.junit.jupiter.params.provider.Arguments; | ||
| import org.junit.jupiter.params.provider.MethodSource; | ||
|
|
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| import java.util.List; | ||
| import java.util.stream.Stream; | ||
|
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| import static org.junit.jupiter.api.Assertions.assertEquals; | ||
|
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| public class Day12Test extends AbstractTest { | ||
|
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| private Day12 solution; | ||
|
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| @BeforeAll | ||
| static void setUp() { | ||
| INPUT_PATH = "year2024/Day12_Input.txt"; | ||
| SAMPLE_INPUT_PATH = "year2024/Day12_SampleInput.txt"; | ||
| } | ||
|
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| @BeforeEach | ||
| void init() { | ||
| solution = new Day12(); | ||
| } | ||
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| @ParameterizedTest | ||
| @MethodSource("inputDataSource") | ||
| void testSolver(Solution.Part part, List<String> inputLines, long expectedSum) { | ||
| long computedSum = solution.solve(part, inputLines); | ||
| assertEquals(expectedSum, computedSum); | ||
| } | ||
|
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| static Stream<Arguments> inputDataSource() { | ||
| List<String> sampleInputLines = getSampleInput(); | ||
| List<String> inputLines = getInput(); | ||
| return Stream.of( | ||
| Arguments.of(Solution.Part.ONE, sampleInputLines, 140), | ||
| Arguments.of(Solution.Part.ONE, inputLines, 1402544), | ||
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| Arguments.of(Solution.Part.TWO, sampleInputLines, 80), | ||
| Arguments.of(Solution.Part.TWO, inputLines, 862486) | ||
| ); | ||
| } | ||
| } |
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