Binary search tree

Author: saarikabhasi

tree/binary-search-tree.py

@@ -0,0 +1,108 @@
+"""
+Binary Search Tree: Binary tree arranged according to binary search property. 
+
+Example:
+            8
+           / \
+          3   10
+        /  \    \
+       1    6     14
+           / \    /
+          4   7  13
+Operations:
+1. Insertion
+2. Insertion of reverse sorted list
+3. Search
+4.is_bst_satisfied : check if tree is BST
+
+"""
+class Node(object):
+    def __init__(self,value):
+        self.value = value
+        self.left = None
+        self.right = None
+
+class BinarySearchTree(object):
+    def __init__(self,root):
+        self.root = Node(root)
+    
+    def insert(self,new_val):
+        self.insert_helper(self.root,new_val)
+
+    def insert_helper(self,current,value):
+        if value <current.value:
+            if current.left:
+                self.insert_helper(current.left,value)
+            else:
+                current.left = Node(value)
+        else: 
+            if current.right:
+                self.insert_helper(current.right,value)
+            else:
+                current.right = Node(value)
+
+        return 
+
+        
+        
+    def search(self,value):
+        return self.search_helper(self.root,value)
+
+    def search_helper(self,current,value):
+        if current:
+            if current.value == value:
+                return True
+            elif value < current.value:
+                return self.search_helper(current.left,value)
+
+            else: 
+                return self.search_helper(current.right,value)
+            
+        return False
+            
+    def is_bst_satisfied(self):    
+        def helper(node,lw=float('-inf'),mx=float('inf')):
+            if not node:
+                return True
+            val = node.value
+
+            if val <= lw:
+                return False
+            if val> mx:
+                return False
+
+            if not helper(node.left,lw,val):
+                return False
+            if not helper(node.right,val,mx):
+                return False
+            return True
+
+
+        
+        return helper(self.root)
+
+
+                
+
+            
+        
+
+
+bst = BinarySearchTree(8)    
+bst.insert(3)
+bst.insert(10)
+bst.insert(1)
+bst.insert(6)
+
+# print(bst.search(19))
+
+bst = BinarySearchTree(10)
+bst.insert(3)
+bst.insert(1)
+bst.insert(25)
+bst.insert(9)
+bst.insert(13)
+
+# print(bst.search(9))
+# print(bst.search(14))
+print(bst.is_bst_satisfied())