Add 669-Trim-a-Binary-Search-Tree.py

python/669-Trim-a-Binary-Search-Tree.py

@@ -0,0 +1,21 @@
+# 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 trimBST(self, root: Optional[TreeNode], low: int, high: int) -> Optional[TreeNode]:
+        if not root:
+            return None
+
+        if root.val > high:
+            return self.trimBST(root.left, low, high)
+
+        if root.val < low:
+            return self.trimBST(root.right, low, high)
+
+        else:
+            root.left = self.trimBST(root.left, low, high)
+            root.right = self.trimBST(root.right, low, high)
+            return root