Create bintree.py

sorting/bintree.py

@@ -0,0 +1,172 @@
+class Node():
+
+	def __init__(self,key):
+		self.key = key
+		self.left = None
+		self.right = None
+		self.parent = None
+		
+
+class Tree():
+
+	def __init__(self):
+		self.root = None		
+
+	def add_node(self,key,node=None):
+
+		if node is None:
+			node = self.root
+		
+		if self.root is None:
+			self.root = Node(key)
+
+		else:
+		
+			if key <= node.key :
+				if node.left is None:
+					node.left = Node(key)
+					node.left.parent = node
+					print "left"
+					return 
+				else:
+					# return self.add_node(key,node = self.root.left)
+					return self.add_node(key,node = node.left)
+			else:
+				if node.right is None:
+					node.right = Node(key)
+					node.right.parent = node
+					print "right"
+					return 
+				else:
+					# return self.add_node(key,node = self.root.right)
+					return self.add_node(key,node = node.right)
+
+	
+	def search(self,key,node = None):
+
+		if node is None:
+			node = self.root
+
+		if self.root.key == key:
+			print "key is at the root"
+			return self.root
+		
+		else:
+			if node.key == key :
+				print "key exists"
+				return node
+
+			elif key < node.key and node.left is not None:
+				print "left"
+				return self.search(key,node = node.left)
+			
+			elif key > node.key and node.right is not None:
+				print "right"
+				return self.search(key,node = node.right)
+			
+			else:
+				print "key does not exist"
+				return None
+
+	def delete_node(self,key,node=None):
+		#search for the node to be deleted in tree
+		if node is None:
+			node = self.search(key)#return the node to be deleted
+
+		#root has no parent node	
+		if self.root.key == node.key: #if it is root
+			parent_node = self.root
+		else:
+			parent_node = node.parent
+			
+
+		'''case 1: The node has no chidren'''
+		if node.left is None and node.right is None:
+			if key <= parent_node.key:
+				parent_node.left = None
+			else:
+				parent_node.right = None
+			return
+
+		'''case 2: The node has children'''
+		''' if it has a single left node'''
+		if node.left is not None and node.right is None :
+			if node.left.key < parent_node.key : 
+				parent_node.left = node.left
+			else:
+				parent_node.right = node.left
+
+			return
+
+		'''if it has a single right node'''
+		if node.right is not None and node.left is None:
+			if node.key <= parent_node.key:
+				parent_node.left = node.right
+			else:
+				parent_node.right = node.right
+			return
+
+		'''if it has two children'''
+		'''find the node with the minimum value from the right subtree.
+		   copy its value to thhe node which needs to be removed.
+		   right subtree now has a duplicate and so remove it.'''
+		if node.left is not None and node.right is not None:
+			min_value = self.find_minimum(node)
+			node.key = min_value.key
+			min_value.parent.left = None
+			return
+
+
+	def find_minimum(self,node = None):
+		
+		if node is None:
+			node = self.root
+
+		'''find mimimum value from the right subtree'''
+		
+		'''case when there is only a root node'''
+		if node.right is not None:
+			node = node.right
+		else:
+			return node
+
+		if node.left is not None:
+			return self.find_minimum(node = node.left)
+		else:
+			return node
+
+	def tree_data(self,node=None):
+		if node is None:
+			node = self.root
+
+		stack = []
+		while stack or node:
+			if node is not None:
+				stack.append(node)
+				node = node.left
+			else:
+				node = stack.pop()
+				yield node.key
+				node = node.right
+
+
+
+		
+			
+t=Tree()
+t.add_node(10)
+t.add_node(13)
+t.add_node(14)
+t.add_node(8)
+t.add_node(9)
+t.add_node(7)
+t.add_node(11)
+
+'''
+10---8---7
+  |	 |
+  |	 ---9
+  ---13---11
+  	   |
+  	   ---14	
+'''