Update README.md

Author: Annatxu

solution/0100-0199/0103.Binary Tree Zigzag Level Order Traversal/README.md

@@ -99,7 +99,7 @@ class Solution:
 
 #### Java
 
-```java
+```java BFS
 /**
  * Definition for a binary tree node.
  * public class TreeNode {
@@ -147,7 +147,22 @@ class Solution {
 }
 ```
 
-```DFS:
+```java DFS
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
 class Solution {
     public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
         List<List<Integer>> result = new ArrayList<>();