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darkmist255
darkmist255 wrote ...

2013/5/1

Pathfinding

darkmist255 darkmist255

2013/5/1

#
So I've got some code here that I whipped up in an attempt to get A* pathfinding to work. It's definitely calculating, but not at all reaching the goal. I haven't yet written any code to get the path, and haven't implemented replacing parents with new, shorter parent paths. For now I'm just hoping I can get atGoal() to return true. The code isn't exactly beautiful but it's fairly neat and legible. Square is a nearly empty class, it just uses Graphics2D to make a visible square.
?
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import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
 
public class PathWorld extends World
{
    final int mult = 20;
    List<Node> open = new ArrayList();
    List<Node> closed = new ArrayList();
    int goalX = 270;
    int goalY = 270;
     
    public PathWorld()
    {
        super(601, 401, 1);
        placeSquares();
        //pathFind(20, 30);
    }
     
    public void placeSquares()
    {
        for(int x = mult/2; x < 600; x = x + mult)
        {
            for(int y = mult/2; y < 400; y = y + mult)
            {
                addObject(new Square(), x, y);
            }
        }
    }
     
    public void pathFind(int startX, int startY)
    {
        Node start = new Node(new coord(startX, startY), null, 0);
        open.add(start);
        addAdj(start);
         
        while(!atGoal())
        {
            Collections.sort(open);
            Node closest = open.get(0);
            for( Node node : closed )
            {
                int a = 1;
                if(node == closest)
                {
                    //if(a > open.size() - 1)
                    closest = open.get(a);
                    a = a + 1;
                }
            }
            addAdj(closest);
        }
    }
     
    public void addAdj(Node n)
    {
        closed.add(n);
        open.remove(n);
        int x = n.getX();
        int y = n.getY();
        int G = n.G;
        Node nt = new Node(x - mult, y - mult, n, G + 28);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x - mult, y, n, G + 20);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x - mult, y + mult, n, G + 28);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x, y - mult, n, G + 20);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x, y + mult, n, G + 20);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x + mult, y - mult, n, G + 28);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x + mult, y, n, G + 20);
        calcHeur(nt);
        checkNode(n, nt);
        nt = new Node(x + mult, y + mult, n, G + 28);
        calcHeur(nt);
        checkNode(n, nt);
    }
     
    public void calcHeur(Node n)
    {
        n.setH((int)Math.sqrt(Math.pow(Math.abs(n.getX() - goalX), 2) + Math.pow(Math.abs(n.getY() - goalY), 2)));
    }
     
    public void checkNode(Node parent, Node nt)
    {
        boolean available = true;
        for( Node node : open )
        {
            if(node.getX() == nt.getX() && node.getY() == nt.getY())
            {
                available = false;
                if(node.G > nt.G)
                {
                    open.remove(node);
                    open.add(nt);
                    break;
                }
            }
        }
        if(available) {open.add(nt);}
    }
     
    public boolean atGoal()
    {
        for( Node node : open )
        {
            if(node.getX() == goalX && node.getY() == goalY)
            {
                return true;
            }
        }
        for( Node node : closed )
        {
            if(node.getX() == goalX && node.getY() == goalY)
            {
                return true;
            }
        }
        return false;
    }
}
Then the accompanying classes:
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public class Node implements Comparable
{
    coord c;
    Node parent;
    int G;
    int H;
    int F;
     
    public Node(coord c, Node p, int G)
    {
        this.c = c;
        this.parent = p;
        this.G = G;
    }
     
    public Node(int x, int y, Node p, int G)
    {
        this.c = new coord(x, y);
        this.parent = p;
        this.G = G;
    }
     
    public void setH(int H)
    {
        this.H = H;
        F = H + G;
    }
     
    public void setG(int G)
    {
        this.G = G;
        F = H + G;
    }
     
    public int getX() { return c.x; }
    public int getY() { return c.y; }
     
    public int compareTo(Object o)
    {
        Node n = (Node)o;
        return this.F - n.F;
    }
}
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public class coord
{
    int x;
    int y;
     
    public coord(int x, int y)
    {
        this.x = x;
        this.y = y;
    }
     
    public boolean atLoc(int x, int y)
    {
        if(this.x == x && this.y == y)
        { return true; }
        else
        return false;
    }
}
If anyone takes a look over this and sees something wrong (I may have messed up compareTo(), since I've never implemented Comparable before), any advice is appreciated!
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