BST vs Hash Map Trade-offs for Ordered Data in DSA C++ - Interactive Comparison Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a key into a Binary Search Tree (BST).

DSA C++

if (root == nullptr) {
    root = new Node([1]);
}

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

Akey

Bvalue

Cnullptr

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'value' instead of 'key' when creating the node.

Assigning 'nullptr' instead of the key.

The BST node is created with the key value when the root is empty.

2fill in blank

medium

Complete the code to check if a key exists in a hash map.

DSA C++

if (hashMap.find([1]) != hashMap.end()) {
    // key exists
}

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

Akey

Bnullptr

ChashMap

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Searching by value instead of key.

Comparing with nullptr instead of end().

We check if the key is present in the hash map by searching for it.

3fill in blank

hard

Fix the error in the BST in-order traversal code to print keys in ascending order.

DSA C++

void inorder(Node* root) {
    if (root == nullptr) return;
    inorder(root->[1]);
    std::cout << root->key << " ";
    inorder(root->right);
}

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

Aright

Bleft

Cparent

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Visiting right child before left child.

Using 'parent' pointer which may not exist.

In-order traversal visits the left child first to print keys in ascending order.

4fill in blank

hard

Fill both blanks to create a hash map that stores keys and their counts only if count is greater than 1.

DSA C++

std::unordered_map<int, int> counts;
for (int num : nums) {
    counts[num]++;
}
auto filtered = [1];
for (auto& pair : counts) {
    if (pair.second [2] 1) {
        filtered[pair.first] = pair.second;
    }
}

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

Astd::unordered_map<int, int>()

B>

C==

Dstd::map<int, int>()

Attempts:

3 left

💡 Hint

Common Mistakes

Using std::map instead of unordered_map for filtered.

Using '==' instead of '>' in the condition.

We initialize an empty unordered_map for filtered results and keep counts greater than 1.

5fill in blank

hard

Fill all three blanks to create a BST node insertion function that inserts keys smaller to the left and larger to the right.

DSA C++

Node* insert(Node* root, int key) {
    if (root == nullptr) {
        return new Node([1]);
    }
    if (key [2] root->key) {
        root->left = insert(root->left, key);
    } else if (key [3] root->key) {
        root->right = insert(root->right, key);
    }
    return root;
}

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

Akey

B<

C>

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' in place of '<' or '>' in comparisons.

Returning nullptr instead of new node.

The function inserts a new node with the key, placing smaller keys to the left and larger keys to the right.