为什么我在Java中实现随机Prim's Algorithm只会生成完整的网格？

Question

我试图在Wikipedia https://en.wikipedia.org/wiki/Maze_generation_algorithmRandomized_Prim的s_algorithm上遵循此伪代码但是我的代码只会生成一个完整的网格。我对算法的功能了解不足。有人可以帮忙解释我在做什么吗？

我看过一些资料，但我无法将其包裹住]

public class MazeGen {
private int dimension, nodeCounter;
private Node[][] nodes;
private List<Edge> walls;

public static void main(String[] args) {
    MazeGen g = new MazeGen(20);
    g.generate();
    g.printMaze();
}

private void generate() {
    pickCell();
    generateMaze();
}

private void generateMaze() {
    while (!walls.isEmpty()) {
        int v;
        Edge wall = walls.get(ThreadLocalRandom.current().nextInt(walls.size()));
        if ((!wall.nodes[0].visited && wall.nodes[1].visited)
                || (wall.nodes[0].visited && !wall.nodes[1].visited)) {
            if (!wall.nodes[0].visited)
                v = 0;
            else
                v = 1;

            includeNode(wall.nodes[v]);
            wall.nodes[Math.abs(v - 1)].visited = true;
        }
        walls.remove(wall);
    }
}

private void pickCell() {
    int i = ThreadLocalRandom.current().nextInt(dimension);
    int j = ThreadLocalRandom.current().nextInt(dimension);

    includeNode(nodes[i][j]);
}

private void includeNode(Node node) {
    node.visited = true;
    node.partOfMaze = true;
    walls.addAll(node.edges);
}

public void printMaze() {
    for (int i = 0; i < dimension; i++) {
        System.out.println();
        for (int j = 0; j < dimension; j++) {
            if (nodes[i][j].partOfMaze) {
                System.out.print(".");
            } else
                System.out.print("p");
        }
    }
}

public MazeGen(int n) {
    nodes = new Node[n][n];
    walls = new ArrayList<Edge>();
    dimension = n;

    createNodes();
    connectAdjacents();
}

private void connectAdjacents() {
    for (int i = 0; i < dimension; i++) {
        for (int j = 0; j < dimension; j++) {
            verifyConnection(i, j, i, j + 1);
            verifyConnection(i, j, i + 1, j);
        }
    }
}

private void verifyConnection(int i, int j, int arg1, int arg2) {
    if (arg1 < dimension && arg2 < dimension)
        connect(i, j, arg1, arg2);
}

private void createNodes() {
    for (int i = 0; i < dimension; i++) {
        for (int j = 0; j < dimension; j++) {
            nodes[i][j] = new Node();
        }
    }
}

private void connect(int row, int col, int row2, int col2) {
    nodes[row][col].edges.add(new Edge(nodes[row][col], nodes[row2][col2]));
    nodes[row2][col2].edges.add(new Edge(nodes[row][col], nodes[row2][col2]));
}

private class Node {
    boolean visited, partOfMaze;
    int number;
    List<Edge> edges;

    Node() {
        number = nodeCounter++;
        edges = new ArrayList<Edge>();
    }

    @Override
    public String toString() {
        return String.valueOf(number);
    }
}

private class Edge {
    Node[] nodes;

    Edge(Node n, Node n2) {
        nodes = new Node[2];
        nodes[0] = n;
        nodes[1] = n2;
    }

    @Override
    public String toString() {
        return nodes[0] + "-" + nodes[1];
    }
}

Answer 1

我认为您的算法是正确的，但您没有保留正确的输出。所有节点都应是迷宫的一部分。应该是迷宫的一部分的墙壁是在处理它们时连接两个访问的节点的墙壁。

制作另一个输出壁数组，并在generateMaze方法中设置值。

private void generateMaze() {
    while (!walls.isEmpty()) {
        int v;
        Edge wall = walls.get(ThreadLocalRandom.current().nextInt(walls.size()));
        if ((!wall.nodes[0].visited && wall.nodes[1].visited)
                || (wall.nodes[0].visited && !wall.nodes[1].visited)) {
            if (!wall.nodes[0].visited)
                v = 0;
            else
                v = 1;

            includeNode(wall.nodes[v]);
            wall.nodes[Math.abs(v - 1)].visited = true;
            /////////////////////////////////////
            // remove this wall from the output walls
            /////////////////////////////////////
        } else {
            ////////////////////////////////
            // add this wall to the output walls
            ////////////////////////////////
        }
        walls.remove(wall);
    }
}