二叉树的序列化与反序列化(Serialize and Deserialize Binary Tree)

比眉伴天荒 2023-02-18 05:29 12阅读 0赞

# 二叉树的序列化与反序列化 #

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.

**Example**:

You may serialize the following tree:
    
        1
       / \
      2   3
         / \
        4   5
    
    as "[1,2,3,null,null,4,5]"

**Clarification**: The above format is the same as how LeetCode 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.

# 思路与代码 #

## Codec ##

public class Codec { 
    
        //序列化
        public String serialize(TreeNode root) {       //用StringBuilder
            StringBuilder res = ser_help(root, new StringBuilder());
            return res.toString();
        }
        
        public StringBuilder ser_help(TreeNode root, StringBuilder str){ 
            if(null == root){ 
                str.append("null,");
                return str;
            }
            str.append(root.val); 
            str.append(",");
            str = ser_help(root.left, str);
            str = ser_help(root.right, str);
            return str;
        }
    
        //反序列化
        public TreeNode deserialize(String data) { 
            String[] str_word = data.split(",");
            List<String> list_word = new LinkedList<String>(Arrays.asList(str_word));
            return deser_help(list_word);
        }
        
        public TreeNode deser_help(List<String> li){ 
            if(li.get(0).equals("null")){ 
                li.remove(0);
                return null;
            }
            TreeNode res = new TreeNode(Integer.valueOf(li.get(0)));
            li.remove(0);
            res.left = deser_help(li);
            res.right = deser_help(li);
            return res;
        }
    }

## TreeNode ##

/** Definition for a binary tree node. */
    public class TreeNode { 
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) {  val = x; }
    }

# test #

//Your Codec object will be instantiated and called as such:
    Codec codec = new Codec();
    codec.deserialize(codec.serialize(root));