array to list: (x,y) to int and int to (x,y)

[migus]

hi,

need help on this:

ned to convert from an array to a list and back.

I wrote this function:

/*
* inputs:
* coordX: column;
* coordY: line;
* nc: number of colums
*
* returns: int
*
*/
 
int XYtoInt(int coordX, int coordY, int nc){
 
     return (coordY * nc + coordX -1);
}

it works fine but the other way arround is giving me sleeping problems.

I was thinking something about this:

/*
* inputs: integer
* returns: X coordinate
*/
int inttoX(int n, int nc){
    int coordX;

    coordX = ...............;

    return coordX;
}

/*
* inputs: integer
* returns: Y coordinate
*/
int inttoY(int n){
    int coordX, coordY;

    coordY = ...............................;
    return coordY;
}

I don't need the code, just na idea to continue... i'm a little blocked.

tanks.
regards

[whiteflags]

OK well you reduced the xy-coordinate with the formula:

reduced = coordY * nc + coordX - 1

The formula needs to be symbolically manipulated to give you the xy-coordinate parts.

coordY = (reduced - coordX + 1) / nc
coordX = reduced - (coordY * nc) + 1

There seems to be no other way. One coordinate requires knowing the other.

[oogabooga]

Assuming x ranges from 0 to nc-1 and the subtraction of one in the XYtoInt function is a mistake, you could simply:

y = n / nc;
x = n % nc;