Improved solving; should now solve all easy puzzles.

[pseudoku.git] / pseudoku / grid / cell.py

diff --git a/pseudoku/grid/cell.py b/pseudoku/grid/cell.py
index 0262130..66eb446 100644 (file)
--- a/pseudoku/grid/cell.py
+++ b/pseudoku/grid/cell.py
@@ -35,47 +35,58 @@ class Cell(object):
     def set(self, value, normalize=True):
         """Sets the value of this cell.  If `normalize` is True or omitted, the
         grid will be updated accordingly.
+
+        Returns the number of cell changes.
         """
         self._values = [value]
         if normalize:
             self._normalized = False
-            self.normalize()
-
+            return self.normalize() + 1
+        
+        return 1
 
 
     def normalize(self):
         """Checks to see if this cell has only one possible value left.  If
         so, sets that as its value and eliminates it from every related cell.
-        This method is exhaustive; that repeated calls should have no effect.
+        This method is exhaustive; repeated calls should have no effect.
+
+        Returns the number of cell changes.
         """
 
         if self._normalized:
             # Already done
-            return
+            return 0
 
         # Set this now just in case of infinite looping
         self._normalized = True
 
         if not self.solved:
             # Don't know the value yet
-            return
+            return 0
 
         # Elimination time
+        cell_changes = 0
         for constraint in self.constraints:
             for cell in constraint.cells:
                 if cell == self:
                     continue
-                cell.eliminate(self.value)
+                cell_changes += cell.eliminate(self.value)
 
+        return cell_changes
 
     def eliminate(self, value):
-        """Eliminates the given value as a possibility for this cell."""
-        if value in self._values:
-            self._values.remove(value)
+        """Eliminates the given value as a possibility for this cell.
+        
+        Returns the number of cell changes."""
+        if value not in self._values:
+            return 0
 
-            if len(self._values) == 0:
-                # XXX give me a real exception here
-                raise Exception
+        self._values.remove(value)
 
-            self._normalized = False
-            self.normalize()
+        if len(self._values) == 0:
+            # XXX give me a real exception here
+            raise Exception
+
+        self._normalized = False
+        return self.normalize() + 1