Bottom View of Binary Tree in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a class for a binary tree node with left and right children.

DSA Typescript

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

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

Anull

Bundefined

C0

Dthis

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined instead of null.

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 add a node to the queue for level order traversal.

DSA Typescript

queue.push({ node: currentNode, hd: [1] });

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

AcurrentNode.value

BhorizontalDistance - 1

C0

DhorizontalDistance + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Subtracting 1 instead of adding for right child.

Using node value instead of distance.

For the right child, horizontal distance increases by 1.

3fill in blank

hard

Fix the error in the code that updates the map with the bottom view node value.

DSA Typescript

map.set(hd, [1]);

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

Ahd

Bnode.left

Cnode.value

Dqueue

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.left or hd as value instead of node.value.

Using queue which is unrelated here.

We store the node's value for the horizontal distance in the map.

4fill in blank

hard

Fill both blanks to complete the loop that processes nodes in the queue.

DSA Typescript

while (queue.length > 0) {
  const { node, hd } = queue.[1]();
  map.set(hd, node.value);
  if (node.left) queue.push({ node: node.left, hd: hd [2] 1 });
  if (node.right) queue.push({ node: node.right, hd: hd + 1 });
}

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

Ashift

Bpop

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() which removes from end, breaking BFS order.

Adding 1 for left child hd instead of subtracting.

Use shift() to dequeue from front; left child hd is hd - 1.

5fill in blank

hard

Fill all three blanks to create the bottom view array from the map.

DSA Typescript

const sortedKeys = Array.from(map.keys()).[1]((a, b) => a [2] b);
const bottomView = sortedKeys.[3](key => map.get(key));

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

Asort

B-

Cmap

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using + instead of - in sort comparator causing wrong order.

Using forEach instead of map for transformation.

Sort keys ascending with sort and subtract; map keys to values with map().