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Serialize and Deserialize a Binary Tree

Certification: Advanced Level Accuracy: 100% Submissions: 2 Points: 10

Write two Python functions to serialize and deserialize a binary tree. Serialization is the process of converting a data structure or object into a sequence of bits (or string) so that it can be stored or transmitted and reconstructed later. Deserialization is the reverse process.

Example 1
    

  • Input:


    Serialize and Deserialize a Binary Tree with three levels

    • 

  • Output: After serialization and deserialization, the tree should be identical to the original tree.
    • 

  • Explanation:
    
      
        
    • Step 1: Traverse the binary tree and serialize it into a string representation.
      • 
        
    • Step 2: Store or transmit the serialized string.
      • 
        
    • Step 3: Deserialize the string back into the original binary tree structure.
      • 
        
    • Step 4: The reconstructed tree is structurally and functionally identical to the original.
      • 
    
    

    •
Example 2
    

  • Input:


     Serialize and Deserialize a Binary Tree with two levels

    • 

  • Output: After serialization and deserialization, the tree should be identical to the original tree.
    • 

  • Explanation:
    
      
        
    • Step 1: Serialize the tree structure starting from root.
      • 
        
    • Step 2: Deserialize to reconstruct the left child and maintain tree hierarchy.
      • 
    
    

    •
Constraints
    

  • Number of nodes in the tree is in the range [0, 10^4]
    • 

  • -1000 ≤ Node.val ≤ 1000
    • 

  • Time Complexity: O(n), where n is the number of nodes
    • 

  • Space Complexity: O(n)
    •
StringsAlgorithmsBinary TreeAccentureEY
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Hint
Solution

Solution Hints

    
  
  • Use level-order traversal (BFS) for serialization
    • 
  
  • Use preorder traversal (DFS) for serialization
    • 
  
  • Use "null" or special marker for null nodes
    • 
  
  • Use a queue for level-order traversal during deserialization
    • 
  
  • Split the string representation for parsing
    •

Steps to solve by this approach:

 Step 1: Create a TreeNode class with value and left/right child pointers.

 Step 2: For serialization, use a preorder traversal (root, left, right) with "null" markers for empty nodes.

 Step 3: Implement a recursive DFS helper function that appends node values to a result list.

 Step 4: Join the values with commas to create a serialized string representation.

 Step 5: For deserialization, split the string by commas and create an iterator.

 Step 6: Implement a recursive function that constructs nodes based on the preorder sequence.

 Step 7: Return null when encountering "null" values, otherwise create a new TreeNode.

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