Diameter of Binary Tree in DSA C++ - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the height of a binary tree node.

DSA C++

int height(TreeNode* node) {
    if (node == nullptr) return 0;
    int leftHeight = height(node->left);
    int rightHeight = height(node->right);
    return 1 + [1];
}

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AleftHeight - rightHeight

Bmin(leftHeight, rightHeight)

CleftHeight + rightHeight

Dmax(leftHeight, rightHeight)

Attempts:

3 left

💡 Hint

Common Mistakes

Using min instead of max for height calculation.

Adding left and right heights instead of taking max.

The height of a node is 1 plus the maximum height of its left and right subtrees.

2fill in blank

medium

Complete the code to update the diameter while computing height.

DSA C++

int diameter = 0;

int height(TreeNode* node) {
    if (node == nullptr) return 0;
    int leftHeight = height(node->left);
    int rightHeight = height(node->right);
    diameter = std::max(diameter, leftHeight + rightHeight + [1]);
    return 1 + std::max(leftHeight, rightHeight);
}

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A0

B-1

C1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Adding 0 instead of 1, missing the current node.

Adding 2 or -1 causing wrong diameter count.

We add 1 to count the current node between left and right paths for diameter.

3fill in blank

hard

Fix the error in the diameter calculation function to return the correct diameter.

DSA C++

int diameterOfBinaryTree(TreeNode* root) {
    diameter = 0;
    height(root);
    return [1];
}

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Adiameter

Bheight(root)

C0

Droot->val

Attempts:

3 left

💡 Hint

Common Mistakes

Returning height instead of diameter.

Returning 0 or root value instead of diameter.

The diameter variable stores the maximum diameter found, so return it.

4fill in blank

hard

Fill both blanks to complete the recursive height function that updates diameter.

DSA C++

int height(TreeNode* node) {
    if (node == nullptr) return 0;
    int leftHeight = height(node->[1]);
    int rightHeight = height(node->[2]);
    diameter = std::max(diameter, leftHeight + rightHeight + 1);
    return 1 + std::max(leftHeight, rightHeight);
}

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Aleft

Bright

Cparent

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Using parent or child which are not valid pointers here.

Swapping left and right causing confusion.

We recursively call height on the left and right child nodes.

5fill in blank

hard

Fill all three blanks to complete the diameter calculation using a helper function.

DSA C++

class Solution {
public:
    int diameter = 0;

    int height(TreeNode* [1]) {
        if ([2] == nullptr) return 0;
        int leftHeight = height([2]->left);
        int rightHeight = height([2]->right);
        diameter = std::max(diameter, leftHeight + rightHeight + 1);
        return 1 + std::max(leftHeight, rightHeight);
    }

    int diameterOfBinaryTree(TreeNode* root) {
        height([3]);
        return diameter - 1;
    }
};

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Anode

Croot

Dthis

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names causing errors.

Calling height with 'this' or wrong variable.

The helper function uses 'node' as parameter and variable; diameterOfBinaryTree calls height with root.