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| 1 | +import java.util.Random; |
| 2 | +import java.util.random.RandomGenerator; |
| 3 | +import java.util.BitSet; |
| 4 | +import java.util.EnumSet; |
| 5 | +import java.util.Set; |
| 6 | + |
| 7 | +import static java.util.stream.IntStream.range; |
| 8 | + |
| 9 | +public class MazeGenerator { |
| 10 | + |
| 11 | + public char[][] generatePerfectMaze(int rows, int columns) { |
| 12 | + validateDimensions(rows, columns); |
| 13 | + return new Grid(new Dimensions(rows, columns), RandomGenerator.getDefault()) |
| 14 | + .generateMaze() |
| 15 | + .placeDoors() |
| 16 | + .print(); |
| 17 | + } |
| 18 | + |
| 19 | + public char[][] generatePerfectMaze(int rows, int columns, int seed) { |
| 20 | + validateDimensions(rows, columns); |
| 21 | + return new Grid(new Dimensions(rows, columns), new Random(seed)) |
| 22 | + .generateMaze() |
| 23 | + .placeDoors() |
| 24 | + .print(); |
| 25 | + } |
| 26 | + |
| 27 | + private void validateDimensions(int rows, int columns) { |
| 28 | + if (rows < 5 || columns < 5 || rows > 100 || columns > 100) { |
| 29 | + throw new IllegalArgumentException("Dimensions must be in range."); |
| 30 | + } |
| 31 | + } |
| 32 | +} |
| 33 | + |
| 34 | +enum Direction { |
| 35 | + NORTH(0, 1), |
| 36 | + EAST(1, 0), |
| 37 | + SOUTH(0, -1), |
| 38 | + WEST(-1, 0); |
| 39 | + private final int dx; |
| 40 | + private final int dy; |
| 41 | + |
| 42 | + Direction(int dx, int dy) { |
| 43 | + this.dx = dx; |
| 44 | + this.dy = dy; |
| 45 | + } |
| 46 | + |
| 47 | + public int dx() { |
| 48 | + return dx; |
| 49 | + } |
| 50 | + |
| 51 | + public int dy() { |
| 52 | + return dy; |
| 53 | + } |
| 54 | +} |
| 55 | + |
| 56 | +final class Grid { |
| 57 | + private final Dimensions dimensions; |
| 58 | + private final BitSet grid; |
| 59 | + private final RandomGenerator randomGenerator; |
| 60 | + |
| 61 | + Grid(Dimensions dimensions, RandomGenerator randomGenerator) { |
| 62 | + this.dimensions = dimensions; |
| 63 | + this.grid = new BitSet(dimensions.width() * dimensions.height()); |
| 64 | + this.randomGenerator = randomGenerator; |
| 65 | + } |
| 66 | + |
| 67 | + Grid generateMaze() { |
| 68 | + generate(new Cell(1, 1)); |
| 69 | + return this; |
| 70 | + } |
| 71 | + |
| 72 | + private int random(int bound) { |
| 73 | + return randomGenerator.nextInt(bound); |
| 74 | + } |
| 75 | + |
| 76 | + private Direction pickRandomDirection(Set<Direction> directions) { |
| 77 | + int size = directions.size(); |
| 78 | + int itemIndex = random(size); |
| 79 | + var direction = directions.toArray(new Direction[size])[itemIndex]; |
| 80 | + directions.remove(direction); |
| 81 | + return direction; |
| 82 | + } |
| 83 | + |
| 84 | + Grid placeDoors() { |
| 85 | + new Cell(1 + 2 * random(dimensions.rows()), 0).erase(); |
| 86 | + new Cell(1 + 2 * random(dimensions.rows()), dimensions.width() - 1).erase(); |
| 87 | + return this; |
| 88 | + } |
| 89 | + |
| 90 | + private void generate(Cell cell) { |
| 91 | + cell.erase(); |
| 92 | + |
| 93 | + var directions = EnumSet.allOf(Direction.class); |
| 94 | + do { |
| 95 | + var direction = pickRandomDirection(directions); |
| 96 | + var wall = cell.move(direction); |
| 97 | + var next = wall.move(direction); |
| 98 | + if (next.isValid() && next.isNotEmpty()) { |
| 99 | + wall.erase(); |
| 100 | + generate(next); |
| 101 | + } |
| 102 | + } while (!directions.isEmpty()); |
| 103 | + } |
| 104 | + |
| 105 | + char[][] print() { |
| 106 | + return range(0, dimensions.height()) |
| 107 | + .mapToObj(this::line) |
| 108 | + .toArray(char[][]::new); |
| 109 | + } |
| 110 | + |
| 111 | + private char[] line(int x) { |
| 112 | + return range(0, dimensions.width()) |
| 113 | + .map(y -> new Cell(x, y).symbol()) |
| 114 | + .collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append) |
| 115 | + .toString() |
| 116 | + .toCharArray(); |
| 117 | + } |
| 118 | + |
| 119 | + private final class Cell { |
| 120 | + final int x; |
| 121 | + final int y; |
| 122 | + |
| 123 | + private Cell(int x, int y) { |
| 124 | + this.x = x; |
| 125 | + this.y = y; |
| 126 | + } |
| 127 | + |
| 128 | + boolean isValid() { |
| 129 | + return x > 0 && x < dimensions.height() && y > 0 && y < dimensions.width(); |
| 130 | + } |
| 131 | + |
| 132 | + void erase() { |
| 133 | + grid.set(index()); |
| 134 | + } |
| 135 | + |
| 136 | + boolean isNotEmpty() { |
| 137 | + return !isEmpty(); |
| 138 | + } |
| 139 | + |
| 140 | + boolean isEmpty() { |
| 141 | + return grid.get(index()); |
| 142 | + } |
| 143 | + |
| 144 | + int index() { |
| 145 | + return x * dimensions.width() + y; |
| 146 | + } |
| 147 | + |
| 148 | + boolean isDoor() { |
| 149 | + return isEmpty() && (y == 0 || y == dimensions.width() - 1); |
| 150 | + } |
| 151 | + |
| 152 | + Cell move(Direction direction) { |
| 153 | + return new Cell(x + direction.dx(), y + direction.dy()); |
| 154 | + } |
| 155 | + |
| 156 | + char symbol() { |
| 157 | + if (isDoor()) { |
| 158 | + return '⇨'; |
| 159 | + } |
| 160 | + if (isEmpty()) { |
| 161 | + return ' '; |
| 162 | + } |
| 163 | + var n = x > 0 && new Cell(x - 1, y).isNotEmpty() ? 1 : 0; |
| 164 | + var e = y < dimensions.width() - 1 && new Cell(x, y + 1).isNotEmpty() ? 1 : 0; |
| 165 | + var s = x < dimensions.height() - 1 && new Cell(x + 1, y).isNotEmpty() ? 1 : 0; |
| 166 | + var w = y > 0 && new Cell(x, y - 1).isNotEmpty() ? 1 : 0; |
| 167 | + var i = n + 2 * e + 4 * s + 8 * w; |
| 168 | + return switch (i) { |
| 169 | + case 0 -> ' '; |
| 170 | + case 1, 5, 4 -> '│'; |
| 171 | + case 2, 8, 10 -> '─'; |
| 172 | + case 3 -> '└'; |
| 173 | + case 6 -> '┌'; |
| 174 | + case 7 -> '├'; |
| 175 | + case 9 -> '┘'; |
| 176 | + case 11 -> '┴'; |
| 177 | + case 12 -> '┐'; |
| 178 | + case 13 -> '┤'; |
| 179 | + case 14 -> '┬'; |
| 180 | + case 15 -> '┼'; |
| 181 | + default -> throw new IllegalStateException("Unexpected value: " + i); |
| 182 | + }; |
| 183 | + } |
| 184 | + } |
| 185 | +} |
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