add serialize and deserialize binary tree solution

Author: Tessa1217

serialize-and-deserialize-binary-tree/Tessa1217.java

@@ -0,0 +1,60 @@
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.Queue;
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+public class Codec {
+
+    private StringBuilder sb = new StringBuilder();
+
+    // Encodes a tree to a single string.
+    public String serialize(TreeNode root) {
+        serializeNode(root);
+        return sb.toString();
+    }
+
+    private void serializeNode(TreeNode node) {
+        // null인 경우 구분 위해 null 문자열 삽입
+        if (node == null) {
+            sb.append("null,");
+            return;
+        }
+        sb.append(node.val).append(",");
+        serializeNode(node.left);
+        serializeNode(node.right);
+    }
+
+    // Decodes your encoded data to tree.
+    public TreeNode deserialize(String data) {
+        String[] dataArr = data.split(",");
+        Queue<String> queue = new LinkedList<>(Arrays.asList(dataArr));
+        return buildTree(queue);
+    }
+
+    private TreeNode buildTree(Queue<String> queue) {
+        String val = queue.poll();
+        if (val.equals("null")) {
+            return null;
+        }
+        TreeNode node = new TreeNode(Integer.parseInt(val));
+        node.left = buildTree(queue);
+        node.right = buildTree(queue);
+
+        return node;
+
+    }
+}
+
+// Your Codec object will be instantiated and called as such:
+// Codec ser = new Codec();
+// Codec deser = new Codec();
+// TreeNode ans = deser.deserialize(ser.serialize(root));
+