- Maximum Depth of Binary Tree #227

Author: ayosecu

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

@@ -0,0 +1,53 @@
+from typing import Optional
+
+# 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:
+    """
+        - Time Complexity: O(n), n = The number of nodes in tree
+        - Space Complexity: O(H), H = The height of tree,
+            - H = logn, if the tree is balanced
+            - H = n, if the tree is skewed
+    """
+    def maxDepth(self, root: Optional[TreeNode]) -> int:
+        if not root:
+            return 0
+        
+        # dfs : count the depth
+        max_depth = 0
+        
+        def dfs(node, count):
+            nonlocal max_depth
+            
+            if not node:
+                max_depth = max(max_depth, count)
+                return
+            
+            dfs(node.left, count + 1)
+            dfs(node.right, count + 1)
+            
+        dfs(root, 0)
+        
+        return max_depth        
+
+def doTest():
+    sol = Solution()
+
+    root1 = TreeNode(3)
+    root1.left = TreeNode(9)
+    root1.right = TreeNode(20)
+    root1.right.left = TreeNode(15)
+    root1.right.right = TreeNode(7)
+    print("TC 1 is Success!" if sol.maxDepth(root1) == 3 else "TC 1 is Failed!")
+
+    root2 = TreeNode(1)
+    root2.right = TreeNode(2)
+    print(f"TC 2 is Success!" if sol.maxDepth(root2) == 2 else "TC 2 is Failed!")
+
+    print(f"TC 3 is Success!" if sol.maxDepth(None) == 0 else "TC 3 is Failed!")
+doTest()