Fix bugs

Author: ChienkuChen

src/_449/449.serialize-and-deserialize-bst.java

@@ -1,4 +1,4 @@
-//package _449;
+package _449;
 
 import java.util.StringTokenizer;
 import java.util.stream.Stream;

src/datastructure/TreeNode.java

@@ -8,4 +8,13 @@ public class TreeNode {
     public TreeNode(int x) {
         val = x;
     }
+
+    @Override
+    public String toString() {
+        return "TreeNode [" +
+                "val=" + val +
+                ", left=" + left +
+                ", right=" + right +
+                "]";
+    }
 }