From 0bf1f22d37b8732a2f8ec74e7eace0068a0c231f Mon Sep 17 00:00:00 2001
From: SiddhantBobde <58205856+SiddhantBobde@users.noreply.github.com>
Date: Fri, 21 Aug 2020 12:25:50 +0530
Subject: [PATCH] Added function for finding K-th smallest element in BST
 (#2318)

* fixes: #2172

* fixes: #2172

* Added docstrings and type of parameters

* fixed error

* Added type hints

* made changes

* removed capital letters from function name

* Added type hints

* fixed bulid error

* modified comments

* fixed build error
---
 data_structures/binary_tree/binary_search_tree.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/data_structures/binary_tree/binary_search_tree.py b/data_structures/binary_tree/binary_search_tree.py
index 386813035..45c3933fe 100644
--- a/data_structures/binary_tree/binary_search_tree.py
+++ b/data_structures/binary_tree/binary_search_tree.py
@@ -141,6 +141,20 @@ class BinarySearchTree:
         else:
             return traversal_function(self.root)
 
+    def inorder(self, arr: list, node: Node):
+        """Perform an inorder traversal and append values of the nodes to
+        a list named arr"""
+        if node:
+            self.inorder(arr, node.left)
+            arr.append(node.value)
+            self.inorder(arr, node.right)
+
+    def find_kth_smallest(self, k: int, node: Node) -> int:
+        """Return the kth smallest element in a binary search tree """
+        arr = []
+        self.inorder(arr, node)  # append all values to list using inorder traversal
+        return arr[k - 1]
+
 
 def postorder(curr_node):
     """