solve: maximum depth of binary tree

Author: JustHm

maximum-depth-of-binary-tree/JustHm.swift

@@ -0,0 +1,11 @@
+// time: O(n) space: O(n)
+class Solution {
+    func maxDepth(_ root: TreeNode?) -> Int {
+        return dfs(root, 1)
+    }
+
+    func dfs(_ node: TreeNode?, _ n: Int) -> Int {
+        guard let node = node else { return n - 1 }
+        return max(dfs(node.left, n+1), dfs(node.right, n+1))
+    }
+}