Added function for finding K-th smallest element in BST

data_structures/binary_tree/binary_search_tree.py

@@ -141,6 +141,28 @@ def traversal_tree(self, traversal_function=None):
         else:
             return traversal_function(self.root)
 
+    def inorder(self, arr, Node):
+        """This function performs inorder traversal and append values of nodes to list named arr
+        Args:-
+        arr -> list
+        Node -> object of class Node
+        """
+        if Node:
+            self.inorder(arr, Node.left)
+            arr.append(Node.value)  # appends values of nodes to list arr
+            self.inorder(arr, Node.right)
+
+    def find_Kth_Smallest(self, k, Node):
+        """ Function return kth smallest element in BST
+        Args:-
+        k -> int
+        Node -> object of class Node
+        Returns:- int
+        """
+        arr = []
+        self.inorder(arr, Node)  # append all values to list using inorder traversal
+        return arr[k - 1]  # returns the kth smallest element in BST
+
 
 def postorder(curr_node):
     """