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docs/notes/37. 序列化二叉树.md

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+# 37. 序列化二叉树
+
+[NowCoder](https://www.nowcoder.com/practice/cf7e25aa97c04cc1a68c8f040e71fb84?tpId=13&tqId=11214&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
+
+## 题目描述
+
+请实现两个函数，分别用来序列化和反序列化二叉树。
+
+## 解题思路
+
+```java
+private String deserializeStr;
+
+public String Serialize(TreeNode root) {
+    if (root == null)
+        return "#";
+    return root.val + " " + Serialize(root.left) + " " + Serialize(root.right);
+}
+
+public TreeNode Deserialize(String str) {
+    deserializeStr = str;
+    return Deserialize();
+}
+
+private TreeNode Deserialize() {
+    if (deserializeStr.length() == 0)
+        return null;
+    int index = deserializeStr.indexOf(" ");
+    String node = index == -1 ? deserializeStr : deserializeStr.substring(0, index);
+    deserializeStr = index == -1 ? "" : deserializeStr.substring(index + 1);
+    if (node.equals("#"))
+        return null;
+    int val = Integer.valueOf(node);
+    TreeNode t = new TreeNode(val);
+    t.left = Deserialize();
+    t.right = Deserialize();
+    return t;
+}
+```