Bottom View of Binary Tree in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new node in the binary tree.

DSA Javascript

class Node {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
}

const root = new Node([1]);

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

Anull

B10

C'root'

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'null' or 'undefined' as the node's data value.

Using a string like 'root' instead of a number.

The root node should be initialized with a numeric value like 10 to represent the data stored in the node.

2fill in blank

medium

Complete the code to add a left child to the root node.

DSA Javascript

root.left = new Node([1]);

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

A5

Bundefined

C'left'

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning 'null' or 'undefined' instead of a new node.

Using a string instead of a number for the node's data.

The left child node should be created with a numeric value like 5 to represent its data.

3fill in blank

hard

Fix the error in the function to calculate the bottom view of the binary tree by completing the missing code.

DSA Javascript

function bottomView(root) {
  if (!root) return [];
  const map = new Map();
  const queue = [];
  queue.push({ node: root, hd: 0 });

  while (queue.length > 0) {
    const { node, hd } = queue.shift();
    map.set(hd, node.data);

    if (node.left) queue.push({ node: node.left, hd: hd [1] 1 });
    if (node.right) queue.push({ node: node.right, hd: hd + 1 });
  }

  const sortedKeys = Array.from(map.keys()).sort((a, b) => a - b);
  return sortedKeys.map(key => map.get(key));
}

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

A/

B+

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '-' for left child's horizontal distance.

Using multiplication or division operators incorrectly.

For the left child, the horizontal distance decreases by 1, so we subtract 1 from hd.

4fill in blank

hard

Fill both blanks to complete the code that updates the map and processes the queue for bottom view calculation.

DSA Javascript

while (queue.length > 0) {
  const { node, hd } = queue.shift();
  map.set([1], [2]);

  if (node.left) queue.push({ node: node.left, hd: hd - 1 });
  if (node.right) queue.push({ node: node.right, hd: hd + 1 });
}

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

Ahd

Bnode.data

Cnode

Dhd + 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using node instead of node.data as map value.

Using hd + 1 as key instead of hd.

The map key is the horizontal distance (hd), and the value is the node's data for bottom view.

5fill in blank

hard

Fill all three blanks to complete the code that returns the bottom view array sorted by horizontal distance.

DSA Javascript

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

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

A-

Bget

C+

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '-' in sort comparator.

Using map.set instead of map.get to retrieve values.

Sorting keys in ascending order uses subtraction (a - b). To get values from map, use map.get(key).