binary-search-tree-iterator add py3 suboptimal soln

0173_binary-search-tree-iterator/python3/extra_space_precompute.py

@@ -0,0 +1,33 @@
+# Time: O(N)
+# Space: O(N)
+
+# 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
+from collections import deque
+
+class BSTIterator:
+    items = None
+
+    def __init__(self, root: Optional[TreeNode]):
+        def inorder(node):
+            return inorder(node.left) + [node.val] + inorder(node.right) if node else []
+        
+        # In-order traversal of a BST gives us values in
+        # sorted order
+        self.items = deque(inorder(root))
+
+    def next(self) -> int:
+        return self.items.popleft()
+
+    def hasNext(self) -> bool:
+        return len(self.items) > 0
+
+
+# Your BSTIterator object will be instantiated and called as such:
+# obj = BSTIterator(root)
+# param_1 = obj.next()
+# param_2 = obj.hasNext()