feat: solve DaleStudy#227 with python

Author: EgonD3V

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

@@ -0,0 +1,80 @@
+from typing import Optional
+from unittest import TestCase, main
+
+
+# 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 maxDepth(self, root: Optional[TreeNode]) -> int:
+        return self.solve_dfs_iterable(root)
+
+    """
+    Runtime: 0 ms (Beats 100.00%)
+    Time Complexity: O(n)
+    > 트리의 모든 노드의 갯수를 n개라고 하면, 트리의 모든 노드를 stack에 넣어 조회하므로 O(n)
+
+    Memory: 17.75 MB (Beats 21.97%)
+    Space Complexity: O(n)
+    > 최악의 경우 트리의 최대 길이가 n인 경우이므로, stack의 최대 크기가 n에 비례하므로 O(n), upper bound
+    """
+    def solve_dfs_iterable(self, root: Optional[TreeNode]) -> int:
+        max_depth = 0
+        stack = [(root, 0)]
+        while stack:
+            curr_node, curr_depth = stack.pop()
+            if curr_node is None:
+                continue
+
+            if curr_node.left is None and curr_node.right is None:
+                max_depth = max(max_depth, curr_depth + 1)
+                continue
+
+            if curr_node.left:
+                stack.append((curr_node.left, curr_depth + 1))
+            if curr_node.right:
+                stack.append((curr_node.right, curr_depth + 1))
+
+        return max_depth
+
+
+    """
+    Runtime: 0 ms (Beats 100.00%)
+    Time Complexity: O(n)
+    
+    Memory: 17.90 MB (Beats 9.05%)
+    Space Complexity: O(n)
+    """
+    def solve_dfs_recursive(self, root: Optional[TreeNode]) -> int:
+        max_depth = 0
+
+        def dfs(node: Optional[TreeNode], depth: int):
+            nonlocal max_depth
+
+            if not node:
+                return max_depth
+
+            if node.left is None and node.right is None:
+                max_depth = max(max_depth, depth + 1)
+                return
+
+            dfs(node.left, depth + 1)
+            dfs(node.right, depth + 1)
+
+        dfs(root, 0)
+
+        return max_depth
+
+
+class _LeetCodeTestCases(TestCase):
+    def test_1(self):
+        self.assertEqual(True, True)
+
+
+if __name__ == '__main__':
+    main()