Create kth Smallest Element in a BST - Leetcode 230.py

Author: gahogg

kth Smallest Element in a BST - Leetcode 230.py

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+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
+        k_ans = [k]
+        ans = [0]
+
+        def dfs(node):
+            if not node:
+                return
+            
+            dfs(node.left)
+            k_ans[0] = k_ans[0] - 1
+
+            if k_ans[0] == 0:
+                ans[0] = node.val
+
+            if k > 0:
+                dfs(node.right)
+            
+        dfs(root)
+        return ans[0]
+        # Time: O(n)
+        # Space: O(n)