another possibility for binary trees with traversals for generators

Author: Mari Wahl

src/trees/binary_tree.py

@@ -6,7 +6,6 @@
 class Node(object):
 
     def __init__(self, item=None,):
-
         self.item = item
         self.left = None
         self.right = None

src/trees/binary_tree_generators.py

@@ -0,0 +1,127 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+class Node(object):
+    def __init__(self, value):
+        self.value = value
+        self.right = None
+        self.left = None
+
+    def add(self, value):
+        new_node = Node(value)
+        if not self.value:
+            self.value = new_node
+        elif not self.left:
+            self.left= new_node
+        elif not self. right:
+            self.right = new_node
+        else:
+            self.left = self.left.add(value)
+
+        return self # without this, it doesn't add!
+
+    def preorder(self):
+        yield self.value
+        if self.left:
+            for node in self.left.preorder():
+                yield node
+        if self.right:
+            for node in self.right.preorder():
+                yield node
+
+    def postorder(self):
+        yield self.value
+        if self.left:
+            for node in self.left.postorder():
+                yield node
+        if self.right:
+            for node in self.right.postorder():
+                yield node
+
+
+    def inorder(self):
+        yield self.value
+        if self.left:
+            for node in self.left.inorder():
+                yield node
+        if self.right:
+            for node in self.right.inorder():
+                yield node
+
+
+    # Another possibility: use an array (a little bit more expensive):
+    def preorder_array(self):
+        nodes = []
+        if self.value:
+            nodes.append(self.value)
+        if self.left:
+            nodes.extend(self.left.preorder_array())
+        if self.right:
+            nodes.extend(self.right.preorder_array())
+        return nodes
+
+
+
+class BT(object):
+    def __init__(self):
+        self.root = None
+
+    def add(self, value):
+        if not self.root:
+            self.root = Node(value)
+        else:
+            self.root.add(value)
+
+    def preorder(self):
+        if self.root:
+            return self.root.preorder()
+        else:
+            return 'Tree is empty.'
+
+    def inorder(self):
+        if self.root:
+            return self.root.inorder()
+        else:
+            return 'Tree is empty.'
+
+    def postorder(self):
+        if self.root:
+            return self.root.postorder()
+        else:
+            return 'Tree is empty.'
+
+    def preorder_array(self):
+        if self.root:
+            return self.root.preorder_array()
+        else:
+            return 'Tree is empty.'
+
+
+
+if __name__ == '__main__':
+    tree = BT()
+
+    for i in range(1, 11):
+        tree.add(i)
+
+    getree = tree.preorder()
+    for i in range(10):
+        print next(getree)
+
+    print
+
+    print tree.preorder_array()
+
+    print
+
+    getree = tree.inorder()
+    for i in range(10):
+        print next(getree)
+
+    print
+
+    getree = tree.postorder()
+    for i in range(10):
+        print next(getree)