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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,113 @@ | ||
| 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.MathUtils; | ||
| import net.bqc.aoc.utils.Pos; | ||
|
|
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| import java.util.*; | ||
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| public class Day20 extends Solution<Long> { | ||
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| private enum Direction { | ||
| NORTH("^", -1, 0), EAST(">", 0, 1), | ||
| SOUTH("v", 1, 0), WEST("<", 0, -1); | ||
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| final String symbol; | ||
| final int dx, dy; | ||
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| Direction(String symbol, int dx, int dy) { | ||
| this.symbol = symbol; | ||
| this.dx = dx; | ||
| this.dy = dy; | ||
| } | ||
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| public static Direction[] nextDirection(Direction d) { | ||
| if (d == null) return new Direction[]{NORTH, EAST, SOUTH, WEST}; | ||
| return switch (d) { | ||
| case NORTH -> new Direction[]{NORTH, EAST, WEST}; | ||
| case SOUTH -> new Direction[]{SOUTH, EAST, WEST}; | ||
| case EAST -> new Direction[]{NORTH, SOUTH, EAST}; | ||
| case WEST -> new Direction[]{NORTH, SOUTH, WEST}; | ||
| }; | ||
| } | ||
| } | ||
|
|
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| private static class PathNode { | ||
| Pos pos; | ||
| long cost; | ||
| Direction direction; | ||
| PathNode prev; | ||
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| public PathNode(Pos pos, long cost, Direction direction) { | ||
| this.pos = pos; | ||
| this.cost = cost; | ||
| this.direction = direction; | ||
| } | ||
| } | ||
|
|
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| @Override | ||
| public Long solve(Part part, List<String> inputLines) { | ||
| super.solve(part, inputLines); | ||
| char[][] map = Array2DUtils.readAsMatrix(inputLines); | ||
| return countCheats(map, isPart2() ? 20 : 2); | ||
| } | ||
|
|
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| private long countCheats(char[][] map, int maxDist) { | ||
| Pos startPos = Array2DUtils.getXPos(map, 'S').get(0); | ||
| Pos endPos = Array2DUtils.getXPos(map, 'E').get(0); | ||
|
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| List<PathNode> initialPath = shortestPath(map, startPos, endPos); | ||
| long initialBestCost = initialPath.get(initialPath.size() - 1).cost; | ||
| long cheatCount = 0; | ||
|
|
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| for (int i = 0; i < initialPath.size() - 1; i++) { | ||
| PathNode pi = initialPath.get(i); | ||
| for (int j = i + 1; j < initialPath.size(); j++) { | ||
| PathNode pj = initialPath.get(j); | ||
| int dist = MathUtils.manhattanDistance(pi.pos.x, pi.pos.y, pj.pos.x, pj.pos.y); | ||
| if (dist <= maxDist && (j - i - dist) >= 100) cheatCount++; | ||
| } | ||
| } | ||
|
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| return cheatCount; | ||
| } | ||
|
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| private List<PathNode> shortestPath(char[][] map, Pos startPos, Pos endPos) { | ||
| PathNode[][] costMap = new PathNode[map.length][map[0].length]; | ||
| costMap[startPos.x][startPos.y] = new PathNode(startPos, 0, Direction.EAST); | ||
|
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| PriorityQueue<PathNode> pq = new PriorityQueue<>((o1, o2) -> (int) (o2.cost - o1.cost)); | ||
| pq.add(costMap[startPos.x][startPos.y]); | ||
| while (!pq.isEmpty()) { | ||
| PathNode curr = pq.poll(); | ||
|
|
||
| for (Direction d : Direction.nextDirection(curr.direction)) { | ||
| int newX = curr.pos.x + d.dx; | ||
| int newY = curr.pos.y + d.dy; | ||
| long nextCost = curr.cost + 1; | ||
|
|
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| if (map[newX][newY] == '#') continue; | ||
|
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| if (costMap[newX][newY] == null) { | ||
| costMap[newX][newY] = new PathNode(new Pos(newX, newY), Long.MAX_VALUE, d); | ||
| } | ||
|
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| if (nextCost < costMap[newX][newY].cost) { | ||
| costMap[newX][newY].cost = nextCost; | ||
| costMap[newX][newY].prev = curr; | ||
| pq.add(costMap[newX][newY]); | ||
| } | ||
| } | ||
| } | ||
|
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| List<PathNode> path = new ArrayList<>(); | ||
| PathNode curr = costMap[endPos.x][endPos.y]; | ||
| while (curr != null) { | ||
| path.add(curr); | ||
| curr = curr.prev; | ||
| } | ||
| Collections.reverse(path); | ||
| return path; | ||
| } | ||
| } |
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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 Day20Test extends AbstractTest { | ||
|
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| private Day20 solution; | ||
|
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| @BeforeAll | ||
| static void setUp() { | ||
| INPUT_PATH = "year2024/Day20_Input.txt"; | ||
| SAMPLE_INPUT_PATH = "year2024/Day20_SampleInput.txt"; | ||
| } | ||
|
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| @BeforeEach | ||
| void init() { | ||
| solution = new Day20(); | ||
| } | ||
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| @ParameterizedTest | ||
| @MethodSource("inputDataSource") | ||
| void testSolver(Solution.Part part, List<String> inputLines, long expectedOutput) { | ||
| long computedOutput = solution.solve(part, inputLines); | ||
| assertEquals(expectedOutput, computedOutput); | ||
| } | ||
|
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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, 0), | ||
| Arguments.of(Solution.Part.ONE, inputLines, 1289), | ||
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| Arguments.of(Solution.Part.TWO, sampleInputLines, 0), | ||
| Arguments.of(Solution.Part.TWO, inputLines, 982425) | ||
| ); | ||
| } | ||
| } |
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