diff --git a/problems/0104.二叉树的最大深度.md b/problems/0104.二叉树的最大深度.md
index 7adb8bb7..cde3d460 100644
--- a/problems/0104.二叉树的最大深度.md
+++ b/problems/0104.二叉树的最大深度.md
@@ -311,6 +311,35 @@ class solution {
 }
 ```
 
+### 559.n叉树的最大深度 
+```java
+class solution {
+    /**
+     * 迭代法，使用层序遍历
+     */
+    public int maxDepth(Node root) {
+        if (root == null)   return 0;
+        int depth = 0;
+        Queue<Node> que = new LinkedList<>();
+        que.offer(root);
+        while (!que.isEmpty())
+        {
+            depth ++;
+            int len = que.size();
+            while (len > 0)
+            {
+                Node node = que.poll();
+                for (int i = 0; i < node.children.size(); i++)
+                    if (node.children.get(i) != null) 
+                        que.offer(node.children.get(i));
+                len--;
+            }
+        }
+        return depth;
+    }
+}
+```
+
 ## python 
 
 ### 104.二叉树的最大深度