feat: WEEK 04 solution (maximum-depth-of-binary-tree)

Author: tigermint

maximum-depth-of-binary-tree/tigermint.kt

@@ -0,0 +1,30 @@
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun maxDepth(root: TreeNode?): Int {
+        if (root == null) return 0
+
+        var maxDepth = 0
+
+        fun dfs(node: TreeNode, depth: Int) {
+            //leaf node
+            if (node.left == null && node.right == null) maxDepth = maxOf(maxDepth, depth)
+
+            if (node.left != null) dfs(node.left!!, depth + 1)
+            if (node.right != null) dfs(node.right!!, depth + 1)
+        }
+
+        dfs(root!!, 1)
+
+        return maxDepth
+    }
+
+}