Serialize and Deserialize Binary Tree in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start serialization by checking if the root is null.

DSA C++

string serialize(TreeNode* root) {
    if (root == [1]) return "#";
    // rest of serialization code
}

Drag options to blanks, or click blank then click option'

ANULL

Bnullptr

C0

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 or NULL instead of nullptr

Checking root == root which is always true

We check if the root pointer is nullptr to know if the tree or subtree is empty.

2fill in blank

medium

Complete the code to append the root value to the serialized string.

DSA C++

string serialize(TreeNode* root) {
    if (root == nullptr) return "#";
    return to_string(root->val) + [1] + serialize(root->left) + [1] + serialize(root->right);
}

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A";"

B" "

C","

D"-"

Attempts:

3 left

💡 Hint

Common Mistakes

Using spaces or semicolons which complicate parsing

No separator causing concatenated values

We use a comma to separate node values in the serialized string for easy splitting later.

3fill in blank

hard

Fix the error in the deserialize helper function to correctly parse the next token.

DSA C++

string nextToken;
getline(ss, [1], ',');

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AnextToken

Btoken

Cvalue

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using an undeclared variable

Using the wrong variable name causing compilation errors

The variable nextToken is used to store the next substring from the stream.

4fill in blank

hard

Fill both blanks to correctly build the tree nodes during deserialization.

DSA C++

if (nextToken == "#") return [1];
int val = stoi(nextToken);
TreeNode* node = new TreeNode(val);
node->left = deserializeHelper(ss);
node->right = [2];
return node;

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Anullptr

BdeserializeHelper(ss)

Cnew TreeNode(val)

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Returning new nodes for null

Not calling deserializeHelper for right subtree

Return nullptr for null nodes and recursively call deserializeHelper for right subtree.

5fill in blank

hard

Fill all three blanks to complete the deserialize function using a stringstream.

DSA C++

TreeNode* deserialize(string data) {
    stringstream [1](data);
    return [2]([3]);
}

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Ass

BdeserializeHelper

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names

Passing string instead of stringstream to helper

Create a stringstream named ss from data and call deserializeHelper(ss) to build the tree.