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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,204 @@ | ||
| import java.util.ArrayDeque; | ||
| import java.util.Deque; | ||
| import java.util.HashMap; | ||
| import java.util.HashSet; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Set; | ||
|
|
||
| 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.solution.Logger; | ||
| import com.github.pareronia.aoc.solution.Sample; | ||
| import com.github.pareronia.aoc.solution.Samples; | ||
| import com.github.pareronia.aoc.solution.SolutionBase; | ||
|
|
||
| public final class AoC2023_23 | ||
| extends SolutionBase<CharGrid, Integer, Integer> { | ||
|
|
||
| private AoC2023_23(final boolean debug) { | ||
| super(debug); | ||
| } | ||
|
|
||
| public static AoC2023_23 create() { | ||
| return new AoC2023_23(false); | ||
| } | ||
|
|
||
| public static AoC2023_23 createDebug() { | ||
| return new AoC2023_23(true); | ||
| } | ||
|
|
||
| @Override | ||
| protected CharGrid parseInput(final List<String> inputs) { | ||
| return CharGrid.from(inputs); | ||
| } | ||
|
|
||
| @Override | ||
| public Integer solvePart1(final CharGrid grid) { | ||
| return new PathFinder(grid, this.debug) | ||
| .findLongestHikeLengthWithDownwardSlopesOnly(); | ||
| } | ||
|
|
||
| @Override | ||
| public Integer solvePart2(final CharGrid grid) { | ||
| return new PathFinder(grid, this.debug).findLongestHikeLength(); | ||
| } | ||
|
|
||
| @Override | ||
| @Samples({ | ||
| @Sample(method = "part1", input = TEST, expected = "94"), | ||
| @Sample(method = "part2", input = TEST, expected = "154"), | ||
| }) | ||
| public void samples() { | ||
| } | ||
|
|
||
| public static void main(final String[] args) throws Exception { | ||
| AoC2023_23.create().run(); | ||
| } | ||
|
|
||
| static final class PathFinder { | ||
| private final CharGrid grid; | ||
| private final Cell start; | ||
| private final Cell end; | ||
| private final Logger logger; | ||
|
|
||
| protected PathFinder(final CharGrid grid, final boolean debug) { | ||
| this.grid = grid; | ||
| this.start = Cell.at(0, 1); | ||
| this.end = Cell.at(grid.getMaxRowIndex(), grid.getMaxColIndex() - 1); | ||
| this.logger = new Logger(debug); | ||
| } | ||
|
|
||
| public int findLongestHikeLength() { | ||
| final Set<Cell> pois = this.findPois(); | ||
| log(pois); | ||
| final Map<Cell, Set<Edge>> graph = this.buildGraph(pois, false); | ||
| log(graph); | ||
| return this.findLongest(graph, start, end, new HashSet<>()); | ||
| } | ||
|
|
||
| public int findLongestHikeLengthWithDownwardSlopesOnly() { | ||
| final Set<Cell> pois = this.findPois(); | ||
| log(pois); | ||
| final Map<Cell, Set<Edge>> graph = this.buildGraph(pois, true); | ||
| log(graph); | ||
| return this.findLongest(graph, start, end, new HashSet<>()); | ||
| } | ||
|
|
||
| private int findLongest( | ||
| final Map<Cell, Set<Edge>> graph, | ||
| final Cell curr, | ||
| final Cell end, | ||
| final Set<Cell> seen | ||
| ) { | ||
| if (curr.equals(end)) { | ||
| return 0; | ||
| } | ||
| int ans = (int) -1e9; | ||
| seen.add(curr); | ||
| for (final Edge e : graph.get(curr)) { | ||
| if (seen.contains(e.vertex)) { | ||
| continue; | ||
| } | ||
| ans = Math.max( | ||
| ans, | ||
| e.weight + this.findLongest(graph, e.vertex, end, seen)); | ||
| } | ||
| seen.remove(curr); | ||
| return ans; | ||
| } | ||
|
|
||
| private Set<Cell> findPois() { | ||
| final Set<Cell> ans = new HashSet<>(); | ||
| this.grid.getCells().forEach(cell -> { | ||
| if (cell.equals(this.start) || cell.equals(this.end)) { | ||
| ans.add(cell); | ||
| return; | ||
| } | ||
| if (this.grid.getValue(cell) == '#') { | ||
| return; | ||
| } | ||
| if (this.grid.getCapitalNeighbours(cell) | ||
| .filter(n -> this.grid.getValue(n) != '#') | ||
| .count() > 2) { | ||
| ans.add(cell); | ||
| } | ||
| }); | ||
| return ans; | ||
| } | ||
|
|
||
| record Edge(Cell vertex, int weight) {} | ||
|
|
||
| private Map<Cell, Set<Edge>> buildGraph( | ||
| final Set<Cell> pois, final boolean downwardSlopesOnly | ||
| ) { | ||
| record State(Cell cell, int distance) {} | ||
|
|
||
| final Map<Cell, Set<Edge>> edges = new HashMap<>(); | ||
| for (final Cell poi : pois) { | ||
| final Deque<State> q = new ArrayDeque<>(Set.of(new State(poi, 0))); | ||
| final Set<Cell> seen = new HashSet<>(Set.of(poi)); | ||
| while (!q.isEmpty()) { | ||
| final State node = q.poll(); | ||
| if (pois.contains(node.cell) && !node.cell.equals(poi)) { | ||
| edges.computeIfAbsent(poi, k -> new HashSet<>()) | ||
| .add(new Edge(node.cell, node.distance)); | ||
| continue; | ||
| } | ||
| for (final Direction d : Direction.CAPITAL) { | ||
| final Cell n = node.cell.at(d); | ||
| if (!this.grid.isInBounds(n)) { | ||
| continue; | ||
| } | ||
| final char val = this.grid.getValue(n); | ||
| if (val == '#') { | ||
| continue; | ||
| } | ||
| if (downwardSlopesOnly | ||
| && Set.of('<', '>', 'v', '^').contains(val) | ||
| && Direction.fromChar(val) != d) { | ||
| continue; | ||
| } | ||
| if (seen.contains(n)) { | ||
| continue; | ||
| } | ||
| seen.add(n); | ||
| q.add(new State(n, node.distance + 1)); | ||
| } | ||
| } | ||
| } | ||
| return edges; | ||
| } | ||
|
|
||
| private void log(final Object obj) { | ||
| this.logger.log(obj); | ||
| } | ||
| } | ||
|
|
||
| private static final String TEST = """ | ||
| #.##################### | ||
| #.......#########...### | ||
| #######.#########.#.### | ||
| ###.....#.>.>.###.#.### | ||
| ###v#####.#v#.###.#.### | ||
| ###.>...#.#.#.....#...# | ||
| ###v###.#.#.#########.# | ||
| ###...#.#.#.......#...# | ||
| #####.#.#.#######.#.### | ||
| #.....#.#.#.......#...# | ||
| #.#####.#.#.#########v# | ||
| #.#...#...#...###...>.# | ||
| #.#.#v#######v###.###v# | ||
| #...#.>.#...>.>.#.###.# | ||
| #####v#.#.###v#.#.###.# | ||
| #.....#...#...#.#.#...# | ||
| #.#########.###.#.#.### | ||
| #...###...#...#...#.### | ||
| ###.###.#.###v#####v### | ||
| #...#...#.#.>.>.#.>.### | ||
| #.###.###.#.###.#.#v### | ||
| #.....###...###...#...# | ||
| #####################.# | ||
| """; | ||
| } |