Boundary Traversal of Binary Tree in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the Node structure for a binary tree.

DSA C++

struct Node {
    int data;
    Node* [1];
    Node* right;
    Node(int val) : data(val), left(nullptr), right(nullptr) {}
};

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

Aleft

Bparent

Cchild

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parent' or 'next' instead of 'left' for the left child pointer.

The left child pointer in a binary tree node is commonly named 'left'.

2fill in blank

medium

Complete the code to check if a node is a leaf node.

DSA C++

bool isLeaf(Node* node) {
    return node != nullptr && node->left == nullptr && node->[1] == nullptr;
}

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

Aparent

Bright

Cchild

Dnext

Attempts:

3 left

💡 Hint

Common Mistakes

Checking wrong pointer names like 'parent' or 'next'.

A leaf node has no left or right children, so both pointers should be nullptr.

3fill in blank

hard

Fix the error in the function to add left boundary nodes (excluding leaves).

DSA C++

void addLeftBoundary(Node* root, vector<int>& res) {
    Node* cur = root->left;
    while (cur != nullptr) {
        if (!isLeaf(cur)) res.push_back(cur->[1]);
        if (cur->left != nullptr) cur = cur->left;
        else cur = cur->right;
    }
}

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

Aright

Bleft

Cdata

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'left' or 'right' instead of 'data' to get the node's value.

To add the node's value, we access the 'data' member, not the child pointers.

4fill in blank

hard

Fill both blanks to add right boundary nodes in reverse order (excluding leaves).

DSA C++

void addRightBoundary(Node* root, vector<int>& res) {
    Node* cur = root->[1];
    vector<int> tmp;
    while (cur != nullptr) {
        if (!isLeaf(cur)) tmp.push_back(cur->[2]);
        if (cur->right != nullptr) cur = cur->right;
        else cur = cur->left;
    }
    for (int i = tmp.size() - 1; i >= 0; --i) res.push_back(tmp[i]);
}

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

Aright

Bleft

Cdata

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from left child or adding pointers instead of values.

Start from the right child of root and add node values (data) to tmp vector.

5fill in blank

hard

Fill in the blank to complete the boundary traversal function.

DSA C++

vector<int> boundaryTraversal(Node* root) {
    vector<int> res;
    if (root == nullptr) return res;
    if (!isLeaf(root)) res.push_back(root->[1]);
    addLeftBoundary(root, res);
    addLeaves(root, res);
    addRightBoundary(root, res);
    return res;
}

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

Adata

Bleft

Cright

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Adding root pointer or child pointers instead of root's value.

The root's value is stored in 'data' and should be added if root is not a leaf.