reorganize dir

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

ebook_src/trees/check_if_bst.py

@@ -0,0 +1,64 @@
+#!/usr/bin/env python
+
+__author__ = "bt3"
+
+
+from binary_search_tree import BST, Node
+from binary_tree import BT, Node
+
+
+def isBST(node, min_node=float("-infinity"), maxVal=float("infinity")):
+    if not node:
+        return True
+
+    if not min_node <= node.item <= maxVal:
+        return False
+
+    return isBST(node.left, min_node, node.item) and \
+           isBST(node.right, node.item, maxVal)
+
+
+
+def isBST_other_method(node, max_node=None, min_node=None):
+
+    if not node:
+        return True
+
+    left, right =  True, True
+    min_node = min_node or float('inf')
+    max_node = max_node or -float('inf')
+
+    if node.left:
+        if node.left.item > node.item or node.left.item > max_node:
+            left = False
+        else:
+            max_node = node.item
+            left =  isBST(node.left, max_node, min_node)
+
+    if node.right:
+        if node.right.item < node.item or node.right.item < min_node:
+            rihjt =  False
+        else:
+            min_node = node.item
+            right =  isBST(node.right, max_node, min_node)
+
+    return left and right
+
+
+
+
+
+if __name__ == '__main__':
+    bt = BST()
+    for i in range(1, 10):
+        bt.add(i)
+
+    assert(isBST(bt.root) == True)
+
+    bt = BT()
+    for i in range(1, 10):
+        bt.add(i)
+
+    assert(isBST(bt.root) == False)
+
+