recursive pathfinding

Hi,
This function is a solution for recursivly finding the lowest cost path between two points in a 2D matrix. the cost of each step is its ".value". it's passed with the cordinates for the start and end points.
However, somethings not working here and I get the wrong results.
i think this is similar to the A* pathfinder but the only examples i have seen are not recurisive...

LARGE is the limit of "long int"

Code:

---

#include "targ62.h"

long int GetMin(Node** matrix,int currentR,int currentC,int endR,int endC,
                                int rows,int columns,Node* father)
{
        long int result;

        //if out of bounds return max of field
        if (currentR==rows || currentC==columns || currentR<0 || currentC<0)
                return LARGE;

        //if reached end
        if (currentC==endC && currentR==endR)
                return (matrix[currentR][currentC].value);

        //if already checked here
        if (matrix[currentR][currentC].status==OPEN)
                return LARGE;

/*record distance from beggining*/
        //if first node
        if (father==NULL)
                //assign first value as best value
                matrix[currentR][currentC].bestFromStart=
                        matrix[currentR][currentC].value;
        //if not first node
        else
        {
                //if bestFromStart old value higher than current value
                if ( (matrix[currentR][currentC].value +
                        father->bestFromStart ) <
                        matrix[currentR][currentC].bestFromStart )
                        //then...
                        matrix[currentR][currentC].bestFromStart=
                                matrix[currentR][currentC].value+                               
                                father->bestFromStart;
                else
                        /*this is a bad path -
                        this way is not shorter than previously found way*/
                        return LARGE;
        }       
       
        //if not reached end       
        matrix[currentR][currentC].status=OPEN;
        result=Smallest4(
                GetMin(matrix,currentR,currentC+1,endR,endC,rows,columns,
                        matrix[currentR,currentC]),
                GetMin(matrix,currentR,currentC-1,endR,endC,rows,columns,
                        matrix[currentR,currentC]),
                GetMin(matrix,currentR+1,currentC,endR,endC,rows,columns,
                        matrix[currentR,currentC]),
                GetMin(matrix,currentR-1,currentC,endR,endC,rows,columns,
                        matrix[currentR,currentC]));

        //set current status to closes- can try here again       
        matrix[currentR][currentC].status=CLOSED;
       
        //if was blocked all directions
        if (result==LARGE)
                return LARGE;

        return matrix[currentR][currentC].value+result;
}

---

the function is called with the following starting parms:

Code:

---

result=GetMin(matrix,startR,startC,endR,endC,rows,columns,NULL);

---

hm..

is matrix[currentR][currentC].bestFromStart already filled at this line?
expecting "value" is a positive number - i would say this statement is never true when matrix[currentR][currentC].bestFromStart is zero

Code:

---

                if ( (matrix[currentR][currentC].value +
                        father->bestFromStart ) <
                        matrix[currentR][currentC].bestFromStart

---

oops, forget to write that all bestFromStart values are initilized to LARGE

:confused: so my best guess is that theres something wrong with matrix[currentR,currentC] <- i'm not sure about that. i'd have used somthing linke &matrix[currentR][currentC]

Code:

---

matrix[currentR,currentC]

---

is definitely, absolutely, wrong. It is the same as

Code:

---

matrix[currentC]

---

(Except it also evalautes currentR and throws away the result).

I expect the compiler will complain about "statement with no effect" or some such if you turn up the warning level sufficiently high.

--
Mas

obviously!!
i should have written

Code:

---

&matrix[currentC][currentR]

---

but it's still not working....
(!!!!!!!!)

what's going wrong?? is there a problem with my logic?

Code:

---

long int GetMin(Node** matrix,int currentR,int currentC,int endR,int endC,
                                int rows,int columns,Node* father)
{
        long int result;

        //if out of bounds return max of field
        if (currentR==rows || currentC==columns || currentR<0 || currentC<0)
                return LARGE;

        //if reached end
        if (currentC==endC && currentR==endR)
                return (matrix[currentR][currentC].value);

        //if already checked here
        if (matrix[currentR][currentC].status==OPEN)
                return LARGE;

/*record distance from beggining*/
        //if first node
        if (father==NULL)
                //assign first value as best value
                matrix[currentR][currentC].bestFromStart=
                        matrix[currentR][currentC].value;
        //if not first node
        else
        {
                //if bestFromStart old value higher than current value
                if ( (matrix[currentR][currentC].value +
                        father->bestFromStart ) <
                        matrix[currentR][currentC].bestFromStart )
                        //then...
                        matrix[currentR][currentC].bestFromStart=
                                matrix[currentR][currentC].value+                               
                                father->bestFromStart;
                else
                        /*this is a bad path -
                        this way is not shorter than previously found way*/
                        return LARGE;
        }       
       
        //if not reached end       
        matrix[currentR][currentC].status=OPEN;
        result=Smallest4(
                GetMin(matrix,currentR,currentC+1,endR,endC,rows,columns,
                &(matrix[currentR][currentC])),
                GetMin(matrix,currentR,currentC-1,endR,endC,rows,columns,
                        &(matrix[currentR][currentC])),
                GetMin(matrix,currentR+1,currentC,endR,endC,rows,columns,
                        &(matrix[currentR][currentC])),
                GetMin(matrix,currentR-1,currentC,endR,endC,rows,columns,
                        &(matrix[currentR][currentC])));

        //set current status to closes- can try here again       
        matrix[currentR][currentC].status=CLOSED;
       
        //if was blocked all directions
        if (result==LARGE)
                return LARGE;

        return matrix[currentR][currentC].value+result;
}

---

can you tell us what u are expecting and what u are getting..?

i gave it a 3X3 matrix when one of the values is -1000 and all the others are 1
looking for a path from 0,0 t0 1,0 i was expecting -991 but got 2

pasted it into my ide - works fine for me (result is -997 in a random matrix setup like yours)