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Serialize and Deserialize Binary Tree

Certification: Advanced Level Accuracy: 0% Submissions: 0 Points: 15

Write a JavaScript program to serialize a binary tree to a string and deserialize a string back to a binary tree. Serialization is the process of converting a data structure into a format that can be stored or transmitted, while deserialization is the reverse process. The serialized string should be able to reconstruct the exact same binary tree structure.

Example 1
    
  
  • Input: root = [1,2,3,null,null,4,5]
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  • Output: "1,2,null,null,3,4,null,null,5,null,null"
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  • Explanation: 
     Step 1: The binary tree has root node 1 with left child 2 and right child 3.

     Step 2: Node 2 has no children (both left and right are null).

     Step 3: Node 3 has left child 4 and right child 5.

     Step 4: Nodes 4 and 5 have no children.

     Step 5: The serialization uses preorder traversal with null markers.
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Example 2
    
  
  • Input: root = [1,2]
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  • Output: "1,2,null,null,null"
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  • Explanation: 
     Step 1: The binary tree has root node 1 with only a left child 2.

     Step 2: Node 2 has no children (both left and right are null).

     Step 3: The right child of root is null.

     Step 4: The serialization captures this structure with null markers.
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Constraints
    
  
  • The number of nodes in the tree is in the range [0, 10^4]
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  • -1000 ≤ Node.val ≤ 1000
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  • Your serialize and deserialize functions should be stateless
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  • The serialized string should be as compact as possible
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  • Time Complexity: O(n) for both serialize and deserialize
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  • Space Complexity: O(n)
    •
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Hint
Solution

Solution Hints

    
  
  • Use preorder traversal (root, left, right) for serialization
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  • Include null markers in the serialized string to preserve tree structure
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  • Use a delimiter (like comma) to separate values in the string
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  • For deserialization, use the same traversal order and a pointer/index
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  • Recursively build the tree while consuming the serialized data
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  • Handle null values properly during reconstruction
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  • Consider using a queue or array with index tracking for deserialization
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Steps to solve by this approach:

 Step 1: For serialization, use preorder traversal (root, left, right) to visit nodes

 Step 2: Convert each node value to string and add null markers for empty nodes

 Step 3: Join all values with a delimiter (comma) to create the serialized string

 Step 4: For deserialization, split the string back into an array of values

 Step 5: Use a global index to track current position in the values array

 Step 6: Recursively build the tree by consuming values in preorder sequence

 Step 7: Handle null values by returning null and incrementing the index

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