vicinity function

Kjeld Petersen: My first version of the vicinity function didn't come out as I attended. Actually it is more or less a influence function, but it should have been a function that would show the vicinity of the last played stone.

I now came up with a more simple version, that will give the correct result.

//all positions has to be unmarked before calling this function

void vicinity(x,y,level)
{
    if( !is_on_board(x,y) || is_marked(x,y) || !level )
    {
        return;
    }
    mark(x,y);
    if( is_empty(x,y) )
    {
        level--;
    }
    vicinity(x+1,y,level);
    vicinity(x-1,y,level);
    vicinity(x,y+1,level);
    vicinity(x,y-1,level);
    return;
}

Kjeld Petersen: Call this function with the coordinate of the last placed stone, and the color of this stone, and the function will return a expression about how many free point this stone has some influence over.

Example:

x = 4;
y = 4;
max=5; //globle variable also used inside the recursive funtion
color = black;

points = vicinity( x,y, count=max, color, hold=false );

The count option is used inside the recursive function, but can be used to set how wide the function should search.

The hold option is used inside the recursive function, and should always be initiated to "false".

vicinity( x,y, count, color, hold )
{
 if( is_not_on_board(x,y) ) return 0
 if( count <= 0 ) return 0
 if( count > max ) return (color_of(x,y)==opposit(color))? 1 : 0
 if( mark_is(x,y) >= count ) return 0
 mark(x,y) = count
 number = 0
 switch position(x,y)
 {
  equal color:
  {
   mark(x,y) = max
   number += vicinity( x+1,y, max, color, hold )
   number += vicinity( x-1,y, max, color, hold )
   number += vicinity( x,y+1, max, color, hold )
   number += vicinity( x,y-1, max, color, hold )
   break
  }
  opposit color:
  {
   number += vicinity( x+1,y, count, color, hold )
   number += vicinity( x-1,y, count, color, hold )
   number += vicinity( x,y+1, count, color, hold )
   number += vicinity( x,y-1, count, color, hold )
   break
  }
  free position:
  {
   if( hold ) return 0
   number++
   around = 0
   around += vicinity( x+1,y, count, color, true )
   around += vicinity( x-1,y, count, color, true )
   around += vicinity( x,y+1, count, color, true )
   around += vicinity( x,y-1, count, color, true )
   if( around )
   {
    number += vicinity( x+1,y, count-1, color, true )
    number += vicinity( x-1,y, count-1, color, true )
    number += vicinity( x,y+1, count-1, color, true )
    number += vicinity( x,y-1, count-1, color, true )
   }
   else
   {
    number += vicinity( x+1,y, count, color, hold )
    number += vicinity( x-1,y, count, color, hold )
    number += vicinity( x,y+1, count, color, hold )
    number += vicinity( x,y-1, count, color, hold )
   }
   break
  }
 return number
}

Vicinity example for the black  

Vicinity example for the black stone  

Vicinity example for the black stone