add solution of maximum-depth-of-binary-tree

Author: jinhyungrhee

maximum-depth-of-binary-tree/jinhyungrhee.java

@@ -0,0 +1,17 @@
+class Solution {
+    public int maxVal;
+    public int maxDepth(TreeNode root) {
+        dfs(root, 0);
+        return maxVal;
+    }
+    public void dfs(TreeNode node, int step) {
+
+        if (node == null) {
+            if (maxVal < step) maxVal = step;
+            return;
+        }
+
+        dfs(node.left, step + 1);
+        dfs(node.right, step + 1);
+    }
+}