Java - nieco mądrzejszy / szybszy
Całkiem trochę kodu. Staram się być szybszy, oceniając pchnięcia w kolejności „jak prawdopodobne jest uwolnienie drogi do skarbu”, która sama w sobie opiera się na dwóch wędrówkach Dijkstry (jeden zatrzymuje się, gdy napotyka skały, drugi ignoruje skały). Działa całkiem nieźle, a ten przykład z pastebinu, który wydaje się być kłopotliwy dla autora, został rozwiązany w około 2 sekund przez tę implementację. Niektóre inne przykłady trwają do 30-40 sekund, co wciąż uważam za zbyt długie, ale nie mogłem znaleźć sposobu, aby to poprawić bez zepsucia rzeczy :)
Podzieliłem swoje rzeczy na kilka plików, aby uzyskać lepszą strukturę (także dlaczego przestawiłem się na Javę z Ruby):
Punkt wejścia:
import java.util.Date;
public class IndianaJones {
public static void main(final String[] args) throws Exception {
final Maze maze = new Maze(System.in);
final Date startAt = new Date();
final int solution = maze.solve();
final Date endAt = new Date();
System.out.printf("Found solution: %s in %d ms.",
solution < Integer.MAX_VALUE ? solution : "X",
endAt.getTime() - startAt.getTime());
}
}
Wyliczanie pomocnika kierunku:
enum Direction {
UP(-1, 0), DOWN(1, 0), LEFT(0, -1), RIGHT(0, 1);
public final int drow;
public final int dcol;
private Direction(final int drow, final int dcol) {
this.drow = drow;
this.dcol = dcol;
}
public final Direction opposite() {
switch (this) {
case UP:
return DOWN;
case DOWN:
return UP;
case LEFT:
return RIGHT;
case RIGHT:
return LEFT;
}
return null;
}
}
Klasa abstrakcyjna reprezentująca zlokalizowaną część „labiryntu”:
abstract class PointOfInterest {
public final int row;
public final int col;
protected PointOfInterest(final int row, final int col) {
this.row = row;
this.col = col;
}
public final boolean isAt(final int row, final int col) {
return this.row == row && this.col == col;
}
@Override
public final String toString() {
return getClass().getSimpleName() + "(" + row + ", " + col + ")";
}
@Override
public final int hashCode() {
return row ^ col;
}
@Override
public final boolean equals(Object obj) {
if (this == obj)
return true;
if (!(obj instanceof PointOfInterest))
return false;
if (!getClass().equals(obj.getClass()))
return false;
final PointOfInterest other = (PointOfInterest) obj;
return row == other.row && col == other.col;
}
}
I wreszcie sam labirynt:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
public class Maze {
private static final char WALL = '1';
private static final char INDY = '2';
private static final char GOAL = '3';
private static final char ROCK = '4';
private final Maze parent;
private final Set<Maze> visited;
private final boolean[][] map;
private final int[][] dijkstra;
private int[][] dijkstraGhost;
private String stringValue = null;
private int shortestSolution = Integer.MAX_VALUE;
private Goal goal = null;
private Indy indy = null;
private Set<Rock> rocks = new HashSet<>();
private Maze(final Maze parent, final Rock rock, final Direction direction) {
this.parent = parent;
this.visited = parent.visited;
map = parent.map;
dijkstra = new int[map.length][map[rock.row].length];
for (final int[] part : dijkstra)
Arrays.fill(part, Integer.MAX_VALUE);
goal = new Goal(parent.goal.row, parent.goal.col);
indy = new Indy(rock.row, rock.col);
for (final Rock r : parent.rocks)
if (r == rock)
rocks.add(new Rock(r.row + direction.drow, r.col + direction.dcol));
else
rocks.add(new Rock(r.row, r.col));
updateDijkstra(goal.row, goal.col, 0, true);
}
public Maze(final InputStream is) {
this.parent = null;
this.visited = new HashSet<>();
try (final BufferedReader br = new BufferedReader(new InputStreamReader(is))) {
String line = br.readLine();
final String[] sizeParts = line.split(" ");
final int height = Integer.parseInt(sizeParts[0]);
final int width = Integer.parseInt(sizeParts[1]);
map = new boolean[height][width];
dijkstra = new int[height][width];
int row = 0;
while ((line = br.readLine()) != null) {
for (int col = 0; col < line.length(); col++) {
final char c = line.charAt(col);
map[row][col] = c == WALL;
dijkstra[row][col] = Integer.MAX_VALUE;
if (c == INDY) {
if (indy != null)
throw new IllegalStateException("Found a second indy!");
indy = new Indy(row, col);
} else if (c == GOAL) {
if (goal != null)
throw new IllegalStateException("Found a second treasure!");
goal = new Goal(row, col);
} else if (c == ROCK) {
rocks.add(new Rock(row, col));
}
}
row++;
}
updateDijkstra(goal.row, goal.col, 0, true);
} catch (final IOException ioe) {
throw new RuntimeException("Could not read maze from InputStream", ioe);
}
}
public int getShortestSolution() {
Maze ptr = this;
while (ptr.parent != null)
ptr = ptr.parent;
return ptr.shortestSolution;
}
public void setShortestSolution(int shortestSolution) {
Maze ptr = this;
while (ptr.parent != null)
ptr = ptr.parent;
ptr.shortestSolution = Math.min(ptr.shortestSolution, shortestSolution);
}
private final boolean isRepeat(final Maze maze) {
return this.visited.contains(maze);
}
private final void updateDijkstra(final int row, final int col, final int value, final boolean force) {
if (row < 0 || col < 0 || row >= dijkstra.length || col >= dijkstra[row].length)
return;
if (map[row][col] || isRockPresent(row, col))
return;
if (dijkstra[row][col] <= value && !force)
return;
dijkstra[row][col] = value;
updateDijkstra(row - 1, col, value + 1, false);
updateDijkstra(row + 1, col, value + 1, false);
updateDijkstra(row, col - 1, value + 1, false);
updateDijkstra(row, col + 1, value + 1, false);
}
private final void updateDijkstraGhost(final int row, final int col, final int value, final boolean force) {
if (row < 0 || col < 0 || row >= dijkstra.length || col >= dijkstra[row].length)
return;
if (map[row][col] || isRockPresent(row, col))
return;
if (dijkstraGhost[row][col] <= value && !force)
return;
dijkstraGhost[row][col] = value;
updateDijkstraGhost(row - 1, col, value + 1, false);
updateDijkstraGhost(row + 1, col, value + 1, false);
updateDijkstraGhost(row, col - 1, value + 1, false);
updateDijkstraGhost(row, col + 1, value + 1, false);
}
private final int dijkstraScore(final int row, final int col) {
if (row < 0 || col < 0 || row >= dijkstra.length || col >= dijkstra[row].length)
return Integer.MAX_VALUE;
return dijkstra[row][col];
}
private final int dijkstraGhostScore(final int row, final int col) {
if (dijkstraGhost == null) {
dijkstraGhost = new int[map.length][map[indy.row].length];
for (final int[] part : dijkstraGhost)
Arrays.fill(part, Integer.MAX_VALUE);
updateDijkstraGhost(goal.row, goal.col, 0, true);
}
if (row < 0 || col < 0 || row >= dijkstra.length || col >= dijkstra[row].length)
return Integer.MAX_VALUE;
return dijkstraGhost[row][col];
}
private boolean isRockPresent(final int row, final int col) {
for (final Rock rock : rocks)
if (rock.isAt(row, col))
return true;
return false;
}
public boolean isEmpty(final int row, final int col) {
if (row < 0 || col < 0 || row >= map.length || col >= map[row].length)
return false;
return !map[row][col] && !isRockPresent(row, col) && !goal.isAt(row, col);
}
public int solve() {
return solve(0);
}
private int solve(final int currentDepth) {
System.out.println(toString());
visited.add(this);
if (isSolved()) {
setShortestSolution(currentDepth);
return 0;
}
if (currentDepth >= getShortestSolution()) {
System.out.println("Aborting at depth " + currentDepth + " because we know better: "
+ getShortestSolution());
return Integer.MAX_VALUE;
}
final Map<Rock, Set<Direction>> nextTries = indy.getMoveableRocks();
int shortest = Integer.MAX_VALUE - 1;
for (final Map.Entry<Rock, Set<Direction>> tries : nextTries.entrySet()) {
final Rock rock = tries.getKey();
for (final Direction dir : tries.getValue()) {
final Maze next = new Maze(this, rock, dir);
if (!isRepeat(next)) {
final int nextSolution = next.solve(currentDepth + 1);
if (nextSolution < shortest)
shortest = nextSolution;
}
}
}
return shortest + 1;
}
public boolean isSolved() {
return indy.canReachTreasure();
}
@Override
public String toString() {
if (stringValue == null) {
final StringBuilder out = new StringBuilder();
for (int row = 0; row < map.length; row++) {
if (row == 0) {
out.append('\u250C');
for (int col = 0; col < map[row].length; col++)
out.append('\u2500');
out.append("\u2510\n");
}
out.append('\u2502');
for (int col = 0; col < map[row].length; col++) {
if (indy.isAt(row, col))
out.append('*');
else if (goal.isAt(row, col))
out.append("$");
else if (isRockPresent(row, col))
out.append("@");
else if (map[row][col])
out.append('\u2588');
else
out.append(base64(dijkstra[row][col]));
}
out.append("\u2502\n");
if (row == map.length - 1) {
out.append('\u2514');
for (int col = 0; col < map[row].length; col++)
out.append('\u2500');
out.append("\u2518\n");
}
}
stringValue = out.toString();
}
return stringValue;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (!obj.getClass().equals(getClass()))
return false;
final Maze other = (Maze) obj;
if (other.map.length != map.length)
return false;
for (int row = 0; row < map.length; row++) {
if (other.map[row].length != map[row].length)
return false;
for (int col = 0; col < map[row].length; col++)
if (other.map[row][col] != map[row][col])
return false;
}
return indy.equals(other.indy) && rocks.equals(other.rocks) && goal.equals(other.goal);
}
@Override
public int hashCode() {
return getClass().hashCode() ^ indy.hashCode() ^ goal.hashCode() ^ rocks.hashCode();
}
private final class Goal extends PointOfInterest {
public Goal(final int row, final int col) {
super(row, col);
}
}
private final class Indy extends PointOfInterest {
public Indy(final int row, final int col) {
super(row, col);
}
public boolean canReachTreasure() {
return dijkstraScore(row, col) < Integer.MAX_VALUE;
}
public SortedMap<Rock, Set<Direction>> getMoveableRocks() {
final SortedMap<Rock, Set<Direction>> out = new TreeMap<>();
@SuppressWarnings("unchecked")
final Set<Direction> checked[][] = new Set[map.length][map[row].length];
lookForRocks(out, checked, row, col, null);
return out;
}
private final void lookForRocks(final Map<Rock, Set<Direction>> rockStore,
final Set<Direction>[][] checked,
final int row,
final int col,
final Direction comingFrom) {
if (row < 0 || col < 0 || row >= checked.length || col >= checked[row].length)
return;
if (checked[row][col] == null)
checked[row][col] = EnumSet.noneOf(Direction.class);
if (checked[row][col].contains(comingFrom))
return;
for (final Rock rock : rocks) {
if (rock.row == row && rock.col == col) {
if (rock.canBeMoved(comingFrom) && rock.isWorthMoving(comingFrom)) {
if (!rockStore.containsKey(rock))
rockStore.put(rock, EnumSet.noneOf(Direction.class));
rockStore.get(rock).add(comingFrom);
}
return;
}
}
if (comingFrom != null)
checked[row][col].add(comingFrom);
for (final Direction dir : Direction.values())
if (comingFrom == null || dir != comingFrom.opposite())
if (isEmpty(row + dir.drow, col + dir.dcol) || isRockPresent(row + dir.drow, col + dir.dcol))
lookForRocks(rockStore, checked, row + dir.drow, col + dir.dcol, dir);
}
}
private final class Rock extends PointOfInterest implements Comparable<Rock> {
public Rock(final int row, final int col) {
super(row, col);
}
public boolean canBeMoved(final Direction direction) {
return isEmpty(row + direction.drow, col + direction.dcol);
}
public boolean isWorthMoving(final Direction direction) {
boolean worthIt = false;
boolean reachable = false;
int emptyAround = 0;
for (final Direction dir : Direction.values()) {
reachable |= (dijkstraScore(row, col) < Integer.MAX_VALUE);
emptyAround += (isEmpty(row + dir.drow, col + dir.dcol) ? 1 : 0);
if (dir != direction && dir != direction.opposite()
&& dijkstraScore(row + dir.drow, col + dir.dcol) < Integer.MAX_VALUE)
worthIt = true;
}
return (emptyAround < 4) && (worthIt || !reachable);
}
public int proximityIndice() {
final int ds = min(dijkstraScore(row - 1, col),
dijkstraScore(row + 1, col),
dijkstraScore(row, col - 1),
dijkstraScore(row, col + 1));
if (ds < Integer.MAX_VALUE)
return ds;
else
return min(dijkstraGhostScore(row - 1, col),
dijkstraGhostScore(row + 1, col),
dijkstraGhostScore(row, col - 1),
dijkstraGhostScore(row, col + 1));
}
@Override
public int compareTo(Rock o) {
return new Integer(proximityIndice()).compareTo(o.proximityIndice());
}
}
private static final char base64(final int i) {
if (i >= 0 && i <= 9)
return (char) ('0' + i);
else if (i < 36)
return (char) ('A' + (i - 10));
else
return ' ';
}
private static final int min(final int i1, final int i2, final int... in) {
int min = Math.min(i1, i2);
for (final int i : in)
min = Math.min(min, i);
return min;
}
}
