last fixes: tree common ancestor

Author: Mari Wahl

src/trees/binary_search_tree.py

@@ -54,10 +54,22 @@ def _printPreorder(self):
         print self.item
 
         if self.left:
-            return self.left._printPreorder()
+            self.left._printPreorder()
 
         if self.right:
-            return self.right._printPreorder()
+            self.right._printPreorder()
+
+    # Another possibility: use an array (a little bit more expensive):
+    def _preorder_array(self):
+        nodes = []
+        if self.item:
+            nodes.append(self.item)
+        if self.left:
+            nodes.extend(self.left._preorder_array())
+        if self.right:
+            nodes.extend(self.right._preorder_array())
+        return nodes
+
 
 
 
@@ -80,6 +92,11 @@ def search(self, value):
         if self.root:
             return self.root._search(value)
 
+    def preorder_array(self):
+        if self.root:
+            return self.root._preorder_array()
+        else:
+            return 'Tree is empty.'
 
 
 if __name__ == '__main__':

src/trees/binary_tree.py

@@ -47,6 +47,14 @@ def _isLeaf(self):
         return not self.right and not self.left
 
 
+    def _preorder(self):
+        print self.item
+        if self.left:
+            self.left._preorder()
+        if self.right:
+            self.right._preorder()
+
+
 
 class BT(object):
 
@@ -61,40 +69,14 @@ def add(self, value):
             self.root._add(value)
 
 
-    def printPreorder(self):
-        current = self.root
-        nodes, stack = [], []
-        while stack or current:
-            if current:
-                nodes.append(current.item) # this is what change
-                stack.append(current)
-                current = current.left
-            else:
-                current = stack.pop()
-                current = current.right
-        print nodes
-
-
-    def printInorder(self):
-        current = self.root
-        nodes, stack = [], []
-        while stack or current:
-
-            if current:
-                stack.append(current)
-                current = current.left
-            else:
-                current = stack.pop()
-                nodes.append(current.item) # this is what change
-                current = current.right
-        print nodes
-
-
     def search(self, value):
         if self.root:
             return self.root._search(value)
 
 
+    def preorder(self):
+        if self.root:
+            return self.root._preorder()
 
 
 if __name__ == '__main__':
@@ -111,7 +93,4 @@ def search(self, value):
 
     print
     print "Printing preorder..."
-    bt.printPreorder()
-
-    print "Printing Inorder..."
-    bt.printInorder()
+    bt.preorder()

src/trees/binary_tree_generators.py

@@ -14,14 +14,22 @@ def add(self, value):
         if not self.value:
             self.value = new_node
         elif not self.left:
-            self.left= new_node
+            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 search(self, item):
+        if self.value == item:
+            return True
+        found = False
+        if (self.left and self.left.search(item)) or \
+                (self.right and self.right.search(item)):
+            found = True
+        return found
+
     def preorder(self):
         yield self.value
         if self.left:
@@ -40,7 +48,6 @@ def postorder(self):
             for node in self.right.postorder():
                 yield node
 
-
     def inorder(self):
         yield self.value
         if self.left:
@@ -50,6 +57,14 @@ def inorder(self):
             for node in self.right.inorder():
                 yield node
 
+    # this is the most basic way to write this function
+    def preorder_simple(self):
+        print self.value
+        if self.left:
+            self.left.preorder_simple()
+        if self.right:
+            self.right.preorder_simple()
+
 
     # Another possibility: use an array (a little bit more expensive):
     def preorder_array(self):
@@ -74,6 +89,12 @@ def add(self, value):
         else:
             self.root.add(value)
 
+    def search(self, item):
+        if self.root:
+            return self.root.search(item)
+        else:
+            return 'Tree is empty.'
+
     def preorder(self):
         if self.root:
             return self.root.preorder()
@@ -98,6 +119,11 @@ def preorder_array(self):
         else:
             return 'Tree is empty.'
 
+    def preorder_simple(self):
+        if self.root:
+            return self.root.preorder_simple()
+        else:
+            return 'Tree is empty.'
 
 
 if __name__ == '__main__':
@@ -106,21 +132,38 @@ def preorder_array(self):
     for i in range(1, 11):
         tree.add(i)
 
+    print 'Searching for node 4'
+    print tree.search(4)
+
+    print 'Searching for node 1'
+    print tree.search(1)
+
+    print 'Searching for node 12'
+    print tree.search(12)
+
+    print 'Pre-order generator...'
     getree = tree.preorder()
     for i in range(10):
         print next(getree)
-
     print
+    print 'Pre-order array...'
 
     print tree.preorder_array()
 
     print
+    print 'Pre-order simple...'
+
+    tree.preorder_simple()
+
+    print
+    print 'Inorder...'
 
     getree = tree.inorder()
     for i in range(10):
         print next(getree)
 
     print
+    print 'Postorder...'
 
     getree = tree.postorder()
     for i in range(10):

src/trees/check_ancestor.py

@@ -4,37 +4,54 @@
 
 
 from binary_search_tree import BST, Node
-from transversal import inorder
-
-def find_ancestor(path, low_value, high_value):
 
+def find_ancestor(path, low_item, high_item):
     while path:
-        current_value = path[0]
+        current_item = path[0]
 
-        if current_value < low_value:
+        if current_item < low_item:
             try:
                 path = path[2:]
             except:
-                return current_value
+                return current_item
 
-        elif current_value > high_value:
+        elif current_item > high_item:
             try:
                 path = path[1:]
             except:
-                return current_value
+                return current_item
 
-        elif low_value <= current_value <= high_value:
-            return current_value
+        elif low_item <= current_item <= high_item:
+            return current_item
 
 
-if __name__ == '__main__':
+def find_ancestor2(tree, n1, n2):
+    if not tree:
+        return False
+
+    if n1 <= tree.item and n2 >= tree.item or (not tree.left and not tree.right) :
+        return tree.item
+
+    if tree.left and (n1 < tree.item and n2 < tree.item):
+        return find_ancestor(tree.left, n1, n2) or tree.item
+
+    if tree.right and (n1 > tree.item and n2 > tree.item):
+        return find_ancestor(tree.right, n1, n2) or tree.item
 
 
+
+if __name__ == '__main__':
     bst = BST()
     l = [10, 5, 6, 3, 8, 2, 1, 11, 9, 4]
     for i in l:
         bst.add(i)
-    nodes = inorder(bst.root)
+    nodes = bst.preorder_array()
+
     print 'Original:    ', l
-    print 'Inorder:     ', nodes
+    print 'Preorder:    ', nodes
+
+    print 'Method 1: '
     print 'Ancestor for 3, 11:', find_ancestor(nodes, 3, 11)
+
+    print 'Method 2: '
+    print 'Ancestor for 3, 11: ', find_ancestor2(bst.root, 3, 11)