solve: W04 maximum depth of binary tree

Author: eunice-hong

maximum-depth-of-binary-tree/eunice-hong.ts

@@ -0,0 +1,31 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+/**
+ * 
+ * Time Complexity: O(n)
+ * Space Complexity: O(n)
+ */
+function maxDepth(root: TreeNode | null): number {
+    if (!root) {
+        // tree is empty
+        return 0
+    } else if (!root.left && !root.right) {
+        // tree has no children
+        return 1
+    } else {
+        // tree has at least one child
+        return 1 + Math.max(maxDepth(root.left), maxDepth(root.right))
+    }
+};