Vertical Order Traversal of Binary Tree in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the map that stores nodes by their vertical column.

DSA Javascript

const columnTable = new Map();

function verticalOrder(root) {
  if (!root) return [];
  const queue = [[root, 0]];
  while (queue.length > 0) {
    const [node, column] = queue.shift();
    if (!columnTable.has([1])) {
      columnTable.set(column, []);
    }
    columnTable.get(column).push(node.val);
    if (node.left) queue.push([node.left, column - 1]);
    if (node.right) queue.push([node.right, column + 1]);
  }
  return Array.from(columnTable.keys()).sort((a, b) => a - b).map(key => columnTable.get(key));
}

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

Aqueue

Bnode

Ccolumn

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for the node object instead of the column number.

Using the root or queue variable incorrectly.

We check if the map has the current column as a key before adding nodes to it.

2fill in blank

medium

Complete the code to add the left child node to the queue with the correct column index.

DSA Javascript

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

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A0

Bcolumn + 1

Ccolumn

Dcolumn - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Adding 1 instead of subtracting 1 for left child.

Using the same column index for left child.

Left child nodes are in the column one less than the current node's column.

3fill in blank

hard

Fix the error in the sorting function to correctly sort the column keys numerically.

DSA Javascript

return Array.from(columnTable.keys()).sort((a, b) => [1]).map(key => columnTable.get(key));

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Aa - b

Bb - a

Ca + b

Da * b

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition or multiplication which does not sort correctly.

Reversing the order by subtracting a from b.

Sorting numerically ascending requires subtracting b from a.

4fill in blank

hard

Fill both blanks to correctly add the right child node to the queue with the updated column index.

DSA Javascript

if (node.right) queue.push([[1], [2]]);

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Anode.right

Bcolumn + 1

Cnode.left

Dcolumn - 1

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.left instead of node.right.

Using column - 1 instead of column + 1 for right child.

Right child node is node.right and its column is current column + 1.

5fill in blank

hard

Fill all three blanks to create a map of columns to sorted node values after traversal.

DSA Javascript

const sortedColumns = Array.from(columnTable.keys()).sort(([1], [2]) => [3]);
const result = sortedColumns.map(key => columnTable.get(key).sort((a, b) => a - b));

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

Aa

Bb

Ca - b

Db - a

Attempts:

3 left

💡 Hint

Common Mistakes

Using b - a which sorts descending.

Mixing parameter names or using incorrect subtraction.

Sort keys by a and b, then subtract b from a for ascending order.