# HG changeset patch
# User Laman
# Date 2017-10-16 22:16:03
# Node ID e79c5818edfd7e47165020e59c86817497510877
# Parent  86543e726ef8521d0cb0f73bf26e577d71c67381

algoritmus X

diff --git a/dlx.py b/dlx.py
new file mode 100644
--- /dev/null
+++ b/dlx.py
@@ -0,0 +1,96 @@
+# based god Donald Knuth
+# http://www-cs-faculty.stanford.edu/~uno/papers/dancing-color.ps.gz
+# sám bych to asi nevymyslel
+
+
+class Cell:
+	def __init__(self,left=None,right=None,up=None,down=None,col=None):
+		self.left=left
+		self.right=right
+		self.up=up
+		self.down=down
+		self.col=col
+
+
+class Column(Cell):
+	def __init__(self,name,*args,**kwargs):
+		super().__init__(*args,**kwargs)
+		self.name=name
+		self.size=0
+
+	def cover(self):
+		self.right.left=self.left
+		self.left.right=self.right
+		r=self.down
+		while r is not self:
+			c=r.right
+			while c is not r:
+				c.down.up=c.up
+				c.up.down=c.down
+				c.col.size-=1
+				c=c.right
+			r=r.down
+
+	def uncover(self):
+		r=self.up
+		while r is not self:
+			c=r.left
+			while c is not r:
+				c.col.size+=1
+				c.down.up=c
+				c.up.down=c
+				c=c.left
+			r=r.up
+		self.right.left=self
+		self.left.right=self
+
+
+class Header:
+	def __init__(self,left=None,right=None):
+		self.left=left
+		self.right=right
+		self._res=[]
+
+	def search(self,k=0):
+		if self.right is self:
+			self.print()
+			return True
+		if len(self._res)<=k:
+			self._res.append(None)
+
+		col=self.chooseCol()
+		col.cover()
+		row=col.down
+		while row is not col:
+			row=row.down
+			self._res[k]=row
+			c=row.right
+			while c is not row:
+				c.col.cover()
+				self.search(k+1)
+				c=row.right
+			c=row.left
+			while c is not row:
+				c.col.uncover()
+				c=c.left
+		col.uncover()
+
+	def chooseCol(self):
+		c=self.right
+		best=c.size
+		res=c
+		while c is not self:
+			if c.size<best:
+				best=c.size
+				res=c
+			c=c.right
+		return res
+
+	def print(self):
+		for r in self._res:
+			c=r.right
+			while c is not r:
+				print(c.col.name,end=" ")
+				c=c.right
+			print()
+		print()
diff --git a/tetris.py b/tetris.py
--- a/tetris.py
+++ b/tetris.py
@@ -74,7 +74,7 @@ def fill(board,pieces):
 				pieces[i][0]-=1
 				partialRes=fill(board,pieces)
 				if partialRes:
-					res+=[((point,v), partialRes)]
+					res.append(((point,v), partialRes))
 				remove(board,point,v)
 				pieces[i][0]+=1
 	return res