Diameter of Binary Tree in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the TreeNode class with left and right children.

DSA Typescript

class TreeNode {
  val: number;
  left: TreeNode | null;
  right: TreeNode | null;
  constructor(val: number) {
    this.val = val;
    this.left = [1];
    this.right = null;
  }
}

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

A0

Bundefined

Cnull

Dthis

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined instead of null for children.

Assigning 0 or this which are incorrect types.

The left child should be initialized to null to indicate no child initially.

2fill in blank

medium

Complete the code to calculate the maximum of two numbers.

DSA Typescript

function max(a: number, b: number): number {
  return a [1];
}

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A+

B> b ? a : b

CMath.max(a, b)

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' which adds numbers instead of comparing.

Using '>' alone which returns a boolean, not a number.

Using Math.max(a, b) inside return without proper syntax.

The ternary operator 'a > b ? a : b' returns the maximum of a and b.

3fill in blank

hard

Fix the error in the recursive function to compute the height of a binary tree node.

DSA Typescript

function height(node: TreeNode | null): number {
  if (node === null) return 0;
  return 1 + Math.max(height(node.left), [1]);
}

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

Anode.left

Bheight(node.left)

Cnode.right

Dheight(node.right)

Attempts:

3 left

💡 Hint

Common Mistakes

Calling height(node.left) twice instead of right child.

Using node.right directly instead of recursive call.

To compute height, we must compare left and right subtree heights recursively.

4fill in blank

hard

Fill both blanks to update the diameter while computing height.

DSA Typescript

function diameterOfBinaryTree(root: TreeNode | null): number {
  let diameter = 0;
  function height(node: TreeNode | null): number {
    if (node === null) return 0;
    const leftHeight = height(node.left);
    const rightHeight = height(node.right);
    diameter = Math.max(diameter, [1] + [2]);
    return 1 + Math.max(leftHeight, rightHeight);
  }
  height(root);
  return diameter;
}

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

AleftHeight

BrightHeight

Cdiameter

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using diameter variable inside Math.max incorrectly.

Adding 1 to heights when updating diameter.

The diameter is updated by the sum of left and right subtree heights at each node.

5fill in blank

hard

Fill all three blanks to complete the diameter calculation function with proper types and return.

DSA Typescript

function diameterOfBinaryTree(root: [1]): [2] {
  let diameter = 0;
  function height(node: [3]): number {
    if (node === null) return 0;
    const leftHeight = height(node.left);
    const rightHeight = height(node.right);
    diameter = Math.max(diameter, leftHeight + rightHeight);
    return 1 + Math.max(leftHeight, rightHeight);
  }
  height(root);
  return diameter;
}

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

ATreeNode | null

Bnumber

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Using void as return type instead of number.

Using TreeNode without null for parameters.

The root parameter and node parameter are TreeNode or null; the function returns a number representing diameter.