Question

Here it is, I have no idea why it doesnt work. Sometimes its ok, sometimes it crashes and sometimes it returns the wrong way…

//apath.h

#ifndef APATH_H
#define APATH_H
#include <vector>
#include <cmath>
#include <memory>
#include <allegro.h>

using namespace std;

double len(int x1, int y1, int x2, int y2);

class GameMap;

class point
{
public:
      int x,y;
      double f,g;
      point *parent;
      point(int _x=0, int _y=0, point *par=NULL) {x=_x; y=_y; parent=par; f=0; g=0;};
      void countF(int sx, int sy, int tx, int ty)
      {
      g=len(x,y,tx,ty);
      f=g+len(sx,sy,x,y);
      };
};

struct point2d
{
      int x,y;
};

//!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
const point2d directions[]=
{
      {1,0},{1,1},{0,1},{-1,1},{-1,0},{-1,-1},{0,-1},{1,-1},
};


class path
{
public:
      vector<point2d> way;
      int step;
      bool findPath(int x, int y, int fx, int fy, GameMap& map, BITMAP* out);
private:
      vector<point> open;
      vector<point> closed;
};


#endif

and apath.cpp:

//apath.cpp

#include "apath.h"
#include <vector>
#include <cmath>



double len(int x1, int y1, int x2, int y2) 
{
       return (sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
       //return max(abs(x1-x2), abs(y1-y2));

      /*int mx=max(x1,x2)-min(x1,x2);
      int my=max(y1,y2)-min(y1,y2);
      return (min(mx,my)*14+max(mx,my)-min(mx,my)*10);*/
};

bool findPoint(vector<point> arr, point pt, point &ret)
{
     for (int i=0; i<arr.size(); i++) if (arr[i].x==pt.x && arr[i].y==pt.y) { ret=arr[i]; return true;}
     return '\0';
};

//GameMap holds the map…

bool path::findPath(int x, int y, int fx, int fy, GameMap& map, BITMAP* out)
{
     while(!open.empty()) open.pop_back();
     while(!closed.empty()) closed.pop_back();
     while(!way.empty()) way.pop_back();

     point start(x,y);
     start.countF(x,y,fx,fy);
     open.push_back(start);

     point finish(fx,fy);

     double min=999999999;
     int index;
     point tmp;
     point *tmp2;
     point comparer;


     while (!findPoint(closed,finish,comparer))
     {
           min=999999999;
           for (int i=0; i<open.size(); i++)
           {
               if(open[i].f<min)
                   {
                       min=open[i].f;
                       index=i;
                   }
           }

           tmp=open[index];
           closed.push_back(open[index]);
           open.erase(open.begin()+index);

           for (int i=0; i<8; i++)
               {
                    tmp2=new point(tmp.x+directions[i].x,tmp.y+directions[i].y);
                    if (map.getCollisionXY(tmp2->x,tmp2->y)==1 // map.getCollision returns 1 when you cant pass through the tile and 0 otherwise...
                    || findPoint(closed,*tmp2,comparer)) continue;
                    if (!findPoint(open,*tmp2,comparer)) 
                    { 
                        point newP(tmp.x+directions[i].x,tmp.y+directions[i].y,&closed[closed.size()-1]);
                        newP.countF(x,y,fx,fy);
                        open.push_back(newP);
                    }
                    else
                    {
                        if (comparer.g>tmp.g)
                        {
                             comparer.parent=&closed[closed.size()-1];
                             comparer.countF(x,y,fx,fy);
                        }
                    }
                    delete tmp2;
               }
/*     for (int i=0; i<open.size(); i++)
        if (open[i].parent!=0)circlefill(out,open[i].x*16+4,open[i].y*16+4,3,0xff0000);
           if (open.empty()) return false;
     for (int i=0; i<closed.size(); i++)
        if (closed[i].parent!=0)circlefill(out,closed[i].x*16+12,closed[i].y*16+12,3,0xffff00);*/ //debug draw

     }
     point2d pt;
     pt.x=finish.x;
     pt.y=finish.y;
     way.push_back(pt);
     point wayer;
     wayer=closed[closed.size()-1];
     while(wayer.parent!=0) //CRASH from here
     {
         wayer=*wayer.parent;
         pt.x=wayer.x;
         pt.y=wayer.y;
         way.push_back(pt);
//         circlefill(out,pt.x*16+12,pt.y*16+12,3,0xffffff); //debug draw
     }    //CRASH to here, i dont exacly know where it is, but when trying to recreate path.
     return true;
};

Some explaination:
GameMap is class with map
and its getCollisionXY returns 1 you cant pass throught tile and 0 otherwise.

Thanx for any help.

Answer 1

One main source I see that could cause access violation is that your points contain parents as pointers and they are members of a vector. If the vector is reallocated these pointers could become invalidated.

Other than that it is hard to immediately see what causes the crash.

You really should run your code through a debugger. I have just pointed out one thing I immediately see.