Maze little problem

Processing Coding Questions
1 
int cols, rows;
int w = 20;

ArrayList<Cell> grid = new ArrayList<Cell>();  
ArrayList<Cell> stack = new ArrayList<Cell>();
Cell current;



void setup() {
  size(820, 820);
  cols = floor(width/w);
  rows = floor(height/w);

  for (int j = 0; j < rows; j++) {
    for (int i = 0; i < cols; i++) {
      Cell cell = new Cell(i, j);
      grid.add(cell);
    }
  }
  //initialized the wall
  for (int j = 0; j < rows/2+1; j++) {
    for (int i = 0; i < cols; i++) {
      grid.get(index(i, j*2 )).wall = true;
    }
  }

  for (int j = 0; j < rows; j++) {
    for (int i = 0; i < cols/2+1; i++) {
      grid.get(index(i*2, j )).wall = true;
    }
  }

  //frameRate(5);
  current = grid.get(index(1, 1));
}



void draw() {
  background(51);
  for (int j = 0; j < rows; j++) {
    for (int i = 0; i < cols; i++) {
      grid.get(index(i, j)).show();
    }
  }
  current.visited = true;
  current.highlight();
  // STEP 1
  Cell next = current.checkNeighbors();
  if (next != null) {
    next.visited = true;

    // STEP 2
    stack.add(current);

    // STEP 3
    removeWalls(current, next);

    // STEP 4
    current = next;
  } else if (stack.size() > 0) {
    current = stack.remove(stack.size()-1);
  }
}



int index(int i, int j) {
  if (i < 0 || j < 0 || i > cols-1 || j > rows-1) {
    return 0;
  }
  return i + j * cols;
}



void removeWalls(Cell a, Cell b) {
  int x = a.i - b.i;
  if (x == 2) {
    grid.get(index((a.i+b.i)/2, a.j)).wall = false;
  } else if (x == -2) {
    grid.get(index((a.i+b.i)/2, a.j)).wall = false;
  }
  int y = a.j - b.j;
  if (y == 2) {
    grid.get(index(a.i, (a.j+b.j)/2)).wall = false;
  } else if (y == -2) {
    grid.get(index(a.i, (a.j+b.j)/2)).wall = false;
  }

}

class Cell {
  int i, j;
  boolean wall = false;
  boolean visited = false;
  
  ArrayList<Cell> neighborAstars = new ArrayList<Cell>();
  
  
  Cell(int i_, int j_) {
    i = i_;
    j = j_;
  }

  
 
  Cell checkNeighbors() {
    ArrayList<Cell> neighbors = new ArrayList<Cell>();

    Cell top    = grid.get(index(i, j-2));
    Cell right  = grid.get(index(i+2, j));
    Cell bottom = grid.get(index(i, j+2));
    Cell left   = grid.get(index(i-2, j));

    if (top != null && !top.visited && !wall) {
      neighbors.add(top);
    }
    if (right != null && !right.visited && !wall) {
      neighbors.add(right);
    }
    if (bottom != null && !bottom.visited && !wall) {
      neighbors.add(bottom);
    } 
    if (left != null && !left.visited && !wall) {
      neighbors.add(left);
    }

    if (neighbors.size() > 0) {
      int r = floor(random(0, neighbors.size()));
      
      return neighbors.get(r);
    } else {
      return null;
    }
  }
  
  
  
    
  
   
   
   void show() {
    int x = i*w;
    int y = j*w;
    stroke(255);
    if(wall){
      noStroke();
      fill(0, 0, 255, 100);
      rect(x, y, w, w);
    }
      if(!wall){
      noStroke();
      fill(255);
      rect(x, y, w, w);
    }
    
    if (visited) {
      noStroke();
      fill(255);
      rect(x, y, w, w);
    }
  }
  
  
 
  void highlight() {
    int x = i*w;
    int y = j*w;
    noStroke();
    fill(0, 0, 255, 100);
    rect(x, y, w, w);

  }
  
  
  

}

why the grid(0,0) always turn wall to !wall.

2

In your index function, you return 0 if i or j are out of bounds.

Since the first cell is at (1, 1) and when you check the neighboring cell at i - 2 and j - 2 you will return the cell at index 0 so the top left one.

Also be careful at your index function. It seems to me that it should be return i + j * rows; (I guess your indices go from top to bottom and then left to right).

1 Like
3

really aperaciate for your carefullness, thanks a lot , it helps.

4

the grid(0,0) is already setted to wall. it means it will never be in arraylist neihbors,there is no way it turn wall to !wall.

and this problem i already fixed out by return 42,but i still confused.can you tell me more details.