[LintCode] Serialize and Deserialize Binary Tree（二叉樹的序列化和反序列化）

時間 2019-11-08

標籤 lintcode serialize deserialize binary tree 二叉樹序列欄目應用數學简体版

原文原文鏈接

描述

設計一個算法，並編寫代碼來序列化和反序列化二叉樹。將樹寫入一個文件被稱爲「序列化」，讀取文件後重建一樣的二叉樹被稱爲「反序列化」。java

如何反序列化或序列化二叉樹是沒有限制的，你只須要確保能夠將二叉樹序列化爲一個字符串，而且能夠將字符串反序列化爲原來的樹結構。node

對二進制樹進行反序列化或序列化的方式沒有限制，LintCode將您的serialize輸出做爲deserialize的輸入，它不會檢查序列化的結果。git

樣例

給出一個測試數據樣例，二叉樹{3,9,20,#,#,15,7}，表示以下的樹結構：github

咱們的數據是進行 BFS 遍歷獲得的。當你測試結果 wrong answer時，你能夠做爲輸入調試你的代碼。算法

你能夠採用其餘的方法進行序列化和反序列化。app

代碼

GitHub 的源代碼，請訪問下面的連接：測試

https://github.com/cwiki-us/java-tutorial/blob/master/src/test/java/com/ossez/lang/tutorial/tests/lintcode/LintCode0007SerializeAndDeserialize.javaui

package com.ossez.lang.tutorial.tests.lintcode;spa

import java.util.ArrayList;.net

import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.ossez.lang.tutorial.models.TreeNode;

/**
* <p>
* 7
* <ul>
* <li>@see <a href=
* "https://www.cwiki.us/display/ITCLASSIFICATION/Serialize+and+Deserialize+Binary+Tree">https://www.cwiki.us/display/ITCLASSIFICATION/Serialize+and+Deserialize+Binary+Tree</a>
* <li>@see<a href=
* "https://www.lintcode.com/problem/serialize-and-deserialize-binary-tree">https://www.lintcode.com/problem/serialize-and-deserialize-binary-tree</a>
* </ul>
* </p>
*
* @author YuCheng
*
*/
public class LintCode0007SerializeAndDeserialize {

   private final static Logger logger = LoggerFactory.getLogger(LintCode0007SerializeAndDeserialize.class);

   /**
   *
   */
   @Test
   public void testMain() {
       logger.debug("BEGIN");
       String data = "{3,9,20,#,#,15,7}";

       System.out.println(serialize(deserialize(data)));

   }

   /**
   * Deserialize from array to tree
   *
   * @param data
   * @return
   */
   private TreeNode deserialize(String data) {
       // NULL CHECK
       if (data.equals("{}")) {
           return null;
       }

       ArrayList<TreeNode> treeList = new ArrayList<TreeNode>();

       data = data.replace("{", "");
       data = data.replace("}", "");
       String[] vals = data.split(",");

       // INSERT ROOT
       TreeNode root = new TreeNode(Integer.parseInt(vals[0]));
       treeList.add(root);

       int index = 0;
       boolean isLeftChild = true;
       for (int i = 1; i < vals.length; i++) {
           if (!vals[i].equals("#")) {
               TreeNode node = new TreeNode(Integer.parseInt(vals[i]));
               if (isLeftChild) {
                   treeList.get(index).left = node;
               } else {
                   treeList.get(index).right = node;
               }
               treeList.add(node);
           }

           // LEVEL
           if (!isLeftChild) {
               index++;
           }

           // MOVE TO RIGHT OR NEXT LEVEL
           isLeftChild = !isLeftChild;
       }

       return root;

   }

   /**
   *
   * @param root
   * @return
   */
   public String serialize(TreeNode root) {
       // write your code here
       if (root == null) {
           return "{}";
       }

       ArrayList<TreeNode> queue = new ArrayList<TreeNode>();
       queue.add(root);

       for (int i = 0; i < queue.size(); i++) {
           TreeNode node = queue.get(i);
           if (node == null) {
               continue;
           }
           queue.add(node.left);
           queue.add(node.right);
       }

       while (queue.get(queue.size() - 1) == null) {
           queue.remove(queue.size() - 1);
       }

       StringBuilder sb = new StringBuilder();
       sb.append("{");
       sb.append(queue.get(0).val);
       for (int i = 1; i < queue.size(); i++) {
           if (queue.get(i) == null) {
               sb.append(",#");
           } else {
               sb.append(",");
               sb.append(queue.get(i).val);
           }
       }
       sb.append("}");
       return sb.toString();
   }

}