Serialize and Deserialize Binary Tree & Serialize and Deserialize BST

最新推荐文章于 2022-10-27 17:34:55 发布

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本文介绍了一种二叉树的序列化和反序列化算法，该算法利用先序遍历的方式将二叉树转换为字符串，并能够从字符串中还原出原始的二叉树结构。

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

as "[1,2,3,null,null,4,5]" , just the same as how LeetCode OJ serializes a binary tree . You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

实现的时候还是参考了提示。发现序列化的时候是正确的，但是反序列化的时候对于存放的结构还不是很清楚，结果找了很长时间。先序遍历，左边的节点会存放在右边的节点前面，所以可以通过递归调用找出父节点的左孩子，然后找出右孩子。每一次取元素是从list的头取出一个元素，正好跟序列化时的顺序相对应。序列化的时候采用先序遍历，先存入父节点，然后把它的左孩子存入，然后再存入他的右孩子。

代码：

public String serialize(TreeNode root) {
        if(root == null){
            return "";
        }
        return sBuilder(root, new StringBuffer());
    }
    //pre order
    private String sBuilder(TreeNode root, StringBuffer sb){
        if(root == null) return "#,";
        sb.append(root.val+",");
        sb.append(sBuilder(root.left, new StringBuffer()));
        sb.append(sBuilder(root.right, new StringBuffer()));
        return sb.toString();
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if(data == null || data.length() == 0) return null;
        String[] split = data.split(",");
        LinkedList<String> nodes = new LinkedList<>(Arrays.asList(split));
        return  dBuilder(nodes);
    }

    private TreeNode dBuilder(LinkedList<String> nodes){
        String val = nodes.remove();
        if(val.equals("#")){
            return null;
        }else{
            TreeNode node = new TreeNode(Integer.parseInt(val));
            node.left = dBuilder(nodes);
            node.right = dBuilder(nodes);
            return node;
        }
    }