Boundary Traversal of Binary Tree in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if a node is a leaf node.

DSA Javascript

function isLeaf(node) {
  return node.left === null && node.[1] === null;
}

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

Aright

Bleft

Cvalue

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Checking only one child instead of both.

Using wrong property names like 'value' or 'parent'.

A node is a leaf if both its left and right children are null. Here, we check if node.right is null.

2fill in blank

medium

Complete the code to add the left boundary nodes (excluding leaves) to the result array.

DSA Javascript

function addLeftBoundary(node, result) {
  let curr = node.left;
  while (curr !== null) {
    if (!isLeaf(curr)) result.push(curr.value);
    curr = curr.[1];
  }
}

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Aright

Bleft

Cparent

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Moving down right child instead of left.

Adding leaf nodes to the boundary.

To traverse the left boundary, move down the left child nodes using curr.left.

3fill in blank

hard

Fix the error in the function that adds leaf nodes to the result array.

DSA Javascript

function addLeaves(node, result) {
  if (node === null) return;
  if (isLeaf(node)) {
    result.push(node.[1]);
    return;
  }
  addLeaves(node.left, result);
  addLeaves(node.right, result);
}

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Aparent

Bleft

Cvalue

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Pushing the left or right child instead of the node's value.

Using undefined properties like 'parent'.

Leaf nodes hold their data in the 'value' property, which should be added to the result.

4fill in blank

hard

Fill both blanks to add the right boundary nodes (excluding leaves) in reverse order.

DSA Javascript

function addRightBoundary(node, result) {
  let curr = node.[1];
  const stack = [];
  while (curr !== null) {
    if (!isLeaf(curr)) stack.push(curr.value);
    curr = curr.[2];
  }
  while (stack.length > 0) {
    result.push(stack.pop());
  }
}

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Aright

Bleft

Cparent

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using left child to start the right boundary.

Not reversing the collected nodes before adding.

Start from the right child and move down right children to collect right boundary nodes in reverse.

5fill in blank

hard

Fill the blank to complete the boundary traversal function.

DSA Javascript

function boundaryTraversal(root) {
  if (root === null) return [];
  const result = [root.[1]];
  addLeftBoundary(root, result);
  addLeaves(root.left, result);
  addLeaves(root.right, result);
  addRightBoundary(root, result);
  return result;
}

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Aslice

Bpush

Cpop

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Adding leaves from root instead of its subtrees.

Wrong order of adding boundaries and leaves.

Forgetting to handle null root.

Start with root's value, add left boundary and leaves from subtrees, then add right boundary to the result array.