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SquidLib platform-independent logic and utility code. Please refer to https://github.com/SquidPony/SquidLib .

There is a newer version: 3.0.6

package squidpony.squidgrid.mapping;


import squidpony.annotation.Beta;
import squidpony.squidgrid.Direction;
import squidpony.squidmath.Coord;
import squidpony.squidmath.GWTRNG;
import squidpony.squidmath.IRNG;

import java.util.ArrayList;

/**
 *
 *
 * Based in part on code from http://weblog.jamisbuck.org/2011/1/27/maze-generation-growing-tree-algorithm
 *
 * @author Eben Howard - http://squidpony.com - [email protected]
 */
@Beta
public class GrowingTreeMazeGenerator {

    private IRNG rng;
    private int width, height;

    public GrowingTreeMazeGenerator(int width, int height) {
        this.width = width;
        this.height = height;
        rng = new GWTRNG();
    }
    public GrowingTreeMazeGenerator(int width, int height, IRNG rng) {
        this.width = width;
        this.height = height;
        this.rng = rng;
    }

    /**
     * Builds and returns a boolean mapping of a maze using the provided chooser method object.
     * 
     * @param choosing the callback object for making the split decision
     * @return 
     */
    public boolean[][] create(ChoosingMethod choosing) {
        boolean[][] map = new boolean[width][height];
        boolean[][] visited = new boolean[width][height];

        int x = rng.nextInt(width / 2);
        int y = rng.nextInt(height / 2);
        x *= 2;
        y *= 2;

        ArrayList deck = new ArrayList<>();
        deck.add(Coord.get(x, y));

        Direction[] dirs = Direction.CARDINALS;
        while (!deck.isEmpty()) {
            int i = choosing.chooseIndex(deck.size());
            Coord p = deck.get(i);
            dirs = rng.shuffle(dirs, new Direction[dirs.length]);

            boolean foundNeighbor = false;
            for (Direction dir : dirs) {
                x = p.x + dir.deltaX * 2;
                y = p.y + dir.deltaY * 2;
                if (x >= 0 && x < width && y >= 0 && y < height) {
                    if (!visited[x][y]) {
                        foundNeighbor = true;
//                        if (rng.nextBoolean()) {
                            visited[x][y] = true;
//                        }
                        map[x][y] = true;
                        map[p.x + dir.deltaX][p.y + dir.deltaY] = true;
                        deck.add(Coord.get(x, y));
                        break;
                    }
                }
            }

            if (!foundNeighbor) {
                deck.remove(p);
            }
        }

        return map;
    }

    public interface ChoosingMethod {

        /**
         * Given the size to choose from, will return a single value smaller than the passed in value and greater than
         * or equal to 0. The value chosen is dependant on the individual implementation.
         *
         * @param size
         * @return
         */
        int chooseIndex(int size);
    }
}