/*
* Several cases considered here.
* First, note that we don't care about any pattern where
* The central square is already clear.
* Rules:
* 1) If clearing the central square increases the number of set regions,
* we cannot thin.
* 2) A "tail" is seen when there are two set flags, including the center.
* Thinning tails would cause paths to shorten so this is disallowed.
* 3) When the cell is surrounded by set cells, it cannot be unset. In this
* case un-setting the cell would not change the number of regions but would
* break topology. There are several such types:
*
* a) @@@ b) @@o c) o@o d) o@o
* @@@ @@@ @@@ @@@
* @@@ @@@ o@o @@o
*
* Type a) is trivial, since it is the case where all cells are set.
* Type b) includes any case where 8 cells are set.
* Type c) is 0 + 2 + 0
* 8 + 16 + 32
* 0 + 128 + 0 = 186 but there are extensions of c) such
* as d) which at the time of writing I do not clearly capture with a
* single rule. d) has 6 set cells so a trial rule for this might be,
* if there are 6 cells or more don't clear (therefore including a,b,c,d)
* but there are several patterns we do want to clear, for example:
*
* o@@
* o@@
* o@@
*
*/
static bool CanThin(bool[,] p, int code)
{
Pattern pattern = new Pattern(p);
int C = pattern.CountSetCells();
if (C == 2)
{
//Debug.Log ("Tail found:\n" + pattern);
return(false);
}
if (C >= 6)
{
//ebug.Log ("6:\n" + pattern);
return(false);
}
//if (C > 6) {
// //Debug.Log ("7 or more:\n" + pattern);
// return false;
//}
//ebug.Log ("PATTERN: "+code+"\n"+pattern);
int n0 = CountRegions(pattern);
pattern.cells [4].value = false;
pattern.ClearLabels();
int n1 = CountRegions(pattern);
//ebug.Log("region count "+n0+" => "+n1);
bool canThin = (n0 == n1);
//ebug.Log ("=> " + canThin);
return(canThin);
}
