[:solved] #227

Author: ppxyn1

maximum-depth-of-binary-tree/ppxyn1.py

@@ -0,0 +1,38 @@
+# idea : DFS
+
+# time : O(n)
+# space : O(n)
+
+class Solution:
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        # edge case 
+        if not root:
+            return 0 
+        max_depth = 0
+        stack = [(root, 1)]
+        while stack:
+            node, depth = stack.pop()
+            max_depth = max(depth, max_depth)
+            if node.left:
+                stack.append((node.left, depth+1))
+            if node.right:
+                stack.append((node.right, depth+1))
+        return max_depth
+
+# another way : Down-top : recursive
+# class Solution:
+#     def maxDepth(self, root: Optional[TreeNode]) -> int:
+#         if not root:
+#             return 0
+#         return 1 + max(
+#         self.maxDepth(root.left),
+#         self.maxDepth(root.right)
+#         )
+
+
+
+
+
+
+
+