Maximum Width of Binary Tree in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue with the root node and its index 0.

DSA Typescript

const queue: Array<[TreeNode | null, number]> = [[[1], 0]];

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Aroot

B0

Cundefined

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using null or undefined instead of root.

Starting with an empty queue.

We start the queue with the root node and index 0 to track positions in the tree.

2fill in blank

medium

Complete the code to calculate the width of the current level.

DSA Typescript

const width = lastIndex - firstIndex + [1];

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A1

B0

C-1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 instead of 1, which undercounts width.

Using 2 or -1, which gives incorrect width.

Width is calculated as last index minus first index plus one to count all nodes in between.

3fill in blank

hard

Fix the error in the code to add child nodes to the queue with correct indices.

DSA Typescript

if (node.left) queue.push([node.left, [1]]);

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Aindex - 1

Bindex + 1

Cindex * 2 + 1

Dindex * 2

Attempts:

3 left

💡 Hint

Common Mistakes

Using index + 1 which is incorrect for left child.

Using index * 2 + 1 which is for right child.

Left child index is calculated as parent index times 2 to maintain position.

4fill in blank

hard

Fill both blanks to add the right child node to the queue with correct index calculation.

DSA Typescript

if (node.right) queue.push([node.right, [1]]);

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Aindex * 2

Bindex + 1

Cindex * 2 + 1

Dindex - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using index * 2 which is for left child.

Using index + 1 which is incorrect for this calculation.

Right child index is parent index times 2 plus 1 to keep correct position.

5fill in blank

hard

Fill all three blanks to complete the function that returns the maximum width of the binary tree.

DSA Typescript

function widthOfBinaryTree(root: TreeNode | null): number {
  if (!root) return 0;
  let maxWidth = 0;
  const queue: Array<[TreeNode, number]> = [[root, 0]];

  while (queue.length > 0) {
    const levelLength = queue.length;
    const firstIndex = queue[0][1];
    const lastIndex = queue[levelLength - 1][1];
    maxWidth = Math.max(maxWidth, lastIndex - firstIndex + [1]);

    for (let i = 0; i < levelLength; i++) {
      const [node, index] = queue.shift()!;
      const normalizedIndex = index - firstIndex;
      if (node.left) queue.push([node.left, normalizedIndex * 2 + [2]]);
      if (node.right) queue.push([node.right, normalizedIndex * 2 + [3]]);
    }
  }

  return maxWidth;
}

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A0

B1

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add 1 in width calculation.

Swapping left and right child index offsets.

Width calculation adds 1; left child index is normalizedIndex * 2 + 0; right child index is normalizedIndex * 2 + 1.