// this boolean function is inside the walker class. It returns if the particle stucks to tree or not.
boolean checkstuck(){
    
    for (int i=0;i<tree.size();i++){
     PVector check=tree.get(i);
      if (abs(PVector.dist(location,check))<=r/2){
        return true;}
      }    
    return false;
 }
 
 
 // this is the main code
 
 void draw(){
  
    
 for (int i=walkers.size()-1;i>=0;i--){
   Walker temp=walkers.get(i);
   temp.move();
    if (temp.checkstuck()){
     tree.add(new PVector(temp.location.x,temp.location.y));
     walkers.remove(i);
     }
 }

 showtree();
}

void showtree(){
 closestdot=tree.size();
 PVector last=tree.get(tree.size()-1);
 stroke(155,255,255);
 strokeWeight(4);
 point(last.x,last.y);
 float olddistance=10000;
 closestdot=tree.size();
  if (tree.size()>4){
    for (int i=0;i<tree.size()-1;i++){
      PVector temptree=tree.get(i);
      distance=abs(PVector.dist(temptree,last));
       if (distance<olddistance){
        closestdot=i;
        olddistance=distance;
       }
    }
   PVector linevector=tree.get(closestdot);
   strokeWeight(1);
   line(last.x,last.y,linevector.x,linevector.y);
  }
}