reorganize dir

Signed-off-by: Mia Steinkirch <mia.steinkirch@gmail.com>

ebook_src/trees/binary_search_tree.py

@@ -0,0 +1,120 @@
+#!/usr/bin/python
+
+__author__ = "bt3"
+
+
+class Node(object):
+
+    def __init__(self, item=None,):
+
+        self.item = item
+        self.left = None
+        self.right = None
+
+    def __repr__(self):
+        return '{}'.format(self.item)
+
+
+    def _add(self, value):
+        new_node = Node(value)
+
+        if not self.item:
+            self.item = new_node
+
+        else:
+            if value > self.item:
+                self.right = self.right and self.right._add(value) or new_node
+            elif value < self.item:
+                self.left = self.left and self.left._add(value) or new_node
+            else:
+                print("BSTs do not support repeated items.")
+
+        return self # this is necessary!!!
+
+
+    def _search(self, value):
+        if self.item == value:
+            return True # or self
+
+        elif self.left and value < self.item:
+                return self.left._search(value)
+
+        elif self.right and value > self.item:
+                return self.right._search(value)
+
+        else:
+            return False
+
+
+    def _isLeaf(self):
+        return not self.right and not self.left
+
+
+    def _printPreorder(self):
+        print self.item
+
+        if self.left:
+            self.left._printPreorder()
+
+        if self.right:
+            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
+
+
+
+
+class BST(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 printPreorder(self):
+        if self.root:
+            self.root._printPreorder()
+
+    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__':
+
+    bst = BST()
+    print "Adding nodes 1 to 10 in the tree..."
+    for i in range(1, 11):
+        bst.add(i)
+
+    print
+    print "Searching for nodes 16 and 6"
+    print bst.search(16)
+    print bst.search(6)
+
+    print
+    print "Printing preorder..."
+    bst.printPreorder()
+
+
+
+