Advent of Code 2022: Day 12

class Vertex { public final int x; public final int y; public final int dist; public final char height; public Vertex(int x, int y, int dist, char height) { this.x = x; this.y = y; this.dist = dist; this.height = height; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Vertex that = (Vertex) o; return x == that.x && y == that.y; } @Override public int hashCode() { return x + y; } @Override public String toString() { return "Vertex{x=" + x + ", y=" + y + ", dist=" + dist + '}'; } } static Vertex findEndPoint(Vertex from, char[][] map) { Set<Vertex> visited = new HashSet<>(); char endMark = 'E'; char nextTraversableMarkAfter_z = '{'; int[][] directions = new int[][]{{-1, 0}, {1, 0}, {0, -1}, {0, 1}}; int mapHeight = map.length; int mapWidth = map[0].length; Vertex start = new Vertex(from.x, from.y, from.dist, from.height); Queue<Vertex> queue = new ArrayDeque<>(); queue.add(start); visited.add(start); while (!queue.isEmpty()) { Vertex current = queue.poll(); for (int[] direction : directions) { int nextX = Math.max(current.x + direction[1], 0); int nextY = Math.max(current.y + direction[0], 0); if (nextX < mapWidth && nextY < mapHeight) { Vertex next = new Vertex(nextX, nextY, current.dist + 1, map[nextY][nextX]); if (!visited.contains(next) && (next.height - current.height <= 1 || current.height == 'S')) { if (next.height == endMark) { map[next.y][next.x] = nextTraversableMarkAfter_z; continue; } if (next.height == nextTraversableMarkAfter_z) { map[next.y][next.x] = endMark; return next; } queue.add(next); visited.add(next); } } } } return new Vertex(from.x, from.y, from.dist, '#'); } static void day12(String puzzleInputUri) throws IOException, InterruptedException { char[][] mapArray = client.send(request.uri((URI.create(puzzleInputUri))).build(), HttpResponse.BodyHandlers.ofLines()) .body() .map(String::toCharArray) .toArray(char[][]::new); System.out.println("Answer 1: " + findEndPoint(new Vertex(0,20,0, 'S'), mapArray)); Vertex answer2 = IntStream.range(0, mapArray.length) .mapToObj(y -> Map.entry(y, mapArray[y])) .flatMap(row -> IntStream.range(0, row.getValue().length) .mapToObj(x -> Stream.of(new Vertex(x, row.getKey(), 0, row.getValue()[x]))) ) .flatMap(Function.identity()) .filter(vertex -> Set.of('a', 'S').contains(vertex.height) && ( (vertex.x == 0 || vertex.x == mapArray[0].length - 1) || (vertex.y == 0 || vertex.y == mapArray.length - 1) ) ) .map(entrance -> findEndPoint(entrance, mapArray)) .filter(v -> v.height != '#') .min(Comparator.comparingInt(v -> v.dist)) .orElseThrow(); System.out.println("Answer 2: " + answer2); }