solves kth largest element in bst

Author: anishLearnsToCode

README.md

@@ -185,7 +185,7 @@
 | 226  | [Invert Binary Tree](https://leetcode.com/problems/invert-binary-tree)                                                                                    |                                  [![Java](assets/java.png)](src/InvertBinaryTree.java) [![Python](assets/python.png)](python/invert_binary_tree.py)                                  |                                                                                                                                   |
 | 227  | [Basic Calculator II](https://leetcode.com/problems/basic-calculator-ii)                                                                                  |                                                                [![Java](assets/java.png)](src/BasicCalculatorII.java)                                                                |                                                                                                                                   |
 | 229  | [Majority Element II](https://leetcode.com/problems/majority-element-ii)                                                                                  |                                                                [![Java](assets/java.png)](src/MajorityElementII.java)                                                                |                                                                                                                                   |
-| 230  | [Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst)                                                              |                                                                                                                                                                                      |                                                                                                                                   |
+| 230  | [Kth Smallest Element in a BST](https://leetcode.com/problems/kth-smallest-element-in-a-bst)                                                              |                                                            [![Java](assets/java.png)](src/KthSmallestElementInABST.java)                                                             |                                                                                                                                   |
 | 231  | [Power of Two](https://leetcode.com/problems/power-of-two)                                                                                                |                                        [![Java](assets/java.png)](src/PowerOf2.java) [![Python](assets/python.png)](python/is_power_of_2.py)                                         |                                                                                                                                   |
 | 232  | [Implement Queue Using Stacks](https://leetcode.com/problems/implement-queue-using-stacks)                                                                |                                 [![Java](assets/java.png)](src/MyQueue.java) [![Python](assets/python.png)](python/implement_queue_using_stacks.py)                                  |                                                                                                                                   |
 | 234  | [Palindrome Linked Lists](https://leetcode.com/problems/palindrome-linked-list)                                                                           |                              [![Java](assets/java.png)](src/PalindromeLinkedList.java) [![Python](assets/python.png)](python/palindrome_linked_list.py)                              |                                                                                                                                   |

src/KthSmallestElementInABST.java

@@ -0,0 +1,27 @@
+// https://leetcode.com/problems/kth-smallest-element-in-a-bst
+// T: O(k + log(N))
+// S: O(log(N))
+
+import java.util.Stack;
+
+public class KthSmallestElementInABST {
+    public int kthSmallest(TreeNode root, int k) {
+        final Stack<TreeNode> stack = new Stack<>();
+        addLeftPathToStack(root, stack);
+
+        for (int count = 0 ; !stack.isEmpty() ; ) {
+            final TreeNode current = stack.pop();
+            count++;
+            if (count == k) return current.val;
+            addLeftPathToStack(current.right, stack);
+        }
+
+        return -1;
+    }
+
+    private void addLeftPathToStack(TreeNode root, Stack<TreeNode> stack) {
+        if (root == null) return;
+        stack.push(root);
+        addLeftPathToStack(root.left, stack);
+    }
+}