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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,120 @@ | ||
| import static java.util.stream.Collectors.toSet; | ||
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| import java.util.ArrayList; | ||
| import java.util.Iterator; | ||
| import java.util.LinkedHashMap; | ||
| import java.util.List; | ||
| import java.util.Map.Entry; | ||
| import java.util.Set; | ||
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| import com.github.pareronia.aoc.CharGrid; | ||
| import com.github.pareronia.aoc.Grid.Cell; | ||
| import com.github.pareronia.aoc.geometry.Direction; | ||
| import com.github.pareronia.aoc.geometry.Turn; | ||
| import com.github.pareronia.aoc.solution.Sample; | ||
| import com.github.pareronia.aoc.solution.Samples; | ||
| import com.github.pareronia.aoc.solution.SolutionBase; | ||
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| public final class AoC2024_06 | ||
| extends SolutionBase<AoC2024_06.Input, Integer, Integer> { | ||
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| private AoC2024_06(final boolean debug) { | ||
| super(debug); | ||
| } | ||
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| public static AoC2024_06 create() { | ||
| return new AoC2024_06(false); | ||
| } | ||
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| public static AoC2024_06 createDebug() { | ||
| return new AoC2024_06(true); | ||
| } | ||
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| @Override | ||
| protected Input parseInput(final List<String> inputs) { | ||
| final CharGrid grid = new CharGrid(inputs); | ||
| final Cell start = grid.getAllEqualTo('^').findFirst().orElseThrow(); | ||
| final Set<Cell> obs = grid.getAllEqualTo('#').collect(toSet()); | ||
| return new Input(grid, obs, start); | ||
| } | ||
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| private Route route( | ||
| final CharGrid grid, final Set<Cell> obs, Cell pos, Direction dir | ||
| ) { | ||
| final LinkedHashMap<Cell, List<Direction>> seen = new LinkedHashMap<>(); | ||
| seen.computeIfAbsent(pos, k -> new ArrayList<>()).add(dir); | ||
| while (true) { | ||
| final Cell nxt = pos.at(dir); | ||
| if (!grid.isInBounds(nxt)) { | ||
| return new Route(false, seen); | ||
| } | ||
| if (obs.contains(nxt)) { | ||
| dir = dir.turn(Turn.RIGHT); | ||
| } else { | ||
| pos = nxt; | ||
| } | ||
| if (seen.containsKey(pos) && seen.get(pos).contains(dir)) { | ||
| return new Route(true, null); | ||
| } | ||
| seen.computeIfAbsent(pos, k -> new ArrayList<>()).add(dir); | ||
| } | ||
| } | ||
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| @Override | ||
| public Integer solvePart1(final Input input) { | ||
| final Route route | ||
| = route(input.grid, input.obs, input.start, Direction.UP); | ||
| return route.path.size(); | ||
| } | ||
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| @Override | ||
| public Integer solvePart2(final Input input) { | ||
| Route route = route(input.grid, input.obs, input.start, Direction.UP); | ||
| final Iterator<Entry<Cell, List<Direction>>> it | ||
| = route.path.entrySet().iterator(); | ||
| Entry<Cell, List<Direction>> prev = it.next(); | ||
| int ans = 0; | ||
| while (it.hasNext()) { | ||
| final Entry<Cell, List<Direction>> curr = it.next(); | ||
| input.obs.add(curr.getKey()); | ||
| final Cell start = prev.getKey(); | ||
| final Direction dir = prev.getValue().remove(0); | ||
| route = route(input.grid, input.obs, start, dir); | ||
| if (route.loop) { | ||
| ans += 1; | ||
| } | ||
| input.obs.remove(curr.getKey()); | ||
| prev = curr; | ||
| } | ||
| return ans; | ||
| } | ||
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| @Override | ||
| @Samples({ | ||
| @Sample(method = "part1", input = TEST, expected = "41"), | ||
| @Sample(method = "part2", input = TEST, expected = "6"), | ||
| }) | ||
| public void samples() { | ||
| } | ||
|
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| public static void main(final String[] args) throws Exception { | ||
| AoC2024_06.create().run(); | ||
| } | ||
|
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| private static final String TEST = """ | ||
| ....#..... | ||
| .........# | ||
| .......... | ||
| ..#....... | ||
| .......#.. | ||
| .......... | ||
| .#..^..... | ||
| ........#. | ||
| #......... | ||
| ......#... | ||
| """; | ||
|
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| record Input(CharGrid grid, Set<Cell> obs, Cell start) {} | ||
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| record Route(boolean loop, LinkedHashMap<Cell, List<Direction>> path) {} | ||
| } |