Tree Traversal Preorder Root Left Right in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to visit the root node first in preorder traversal.

DSA Javascript

function preorder(node) {
  if (node == null) return;
  console.log(node.value);
  preorder(node[1]);
}

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

A.left

B.right

C.parent

D.child

Attempts:

3 left

💡 Hint

Common Mistakes

Using .right instead of .left causes wrong traversal order.

Trying to access .parent instead of children.

In preorder traversal, after visiting the root, we visit the left child first.

2fill in blank

medium

Complete the code to visit the right child after the left child in preorder traversal.

DSA Javascript

function preorder(node) {
  if (node == null) return;
  console.log(node.value);
  preorder(node.left);
  preorder(node[1]);
}

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

A.right

B.left

C.parent

D.child

Attempts:

3 left

💡 Hint

Common Mistakes

Visiting .left twice instead of .right second time.

Trying to visit .parent or .child which are not correct.

After visiting the root and left subtree, preorder visits the right subtree.

3fill in blank

hard

Fix the error in the preorder traversal code to correctly visit root, left, then right.

DSA Javascript

function preorder(node) {
  if (node == null) return;
  console.log(node.value);
  preorder(node.left);
  preorder(node[1]);
}

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

A.left

B.right

C.parent

D.child

Attempts:

3 left

💡 Hint

Common Mistakes

Calling preorder on .left twice.

Using .parent or .child which are invalid here.

The second recursive call must visit the right child to follow preorder traversal order.

4fill in blank

hard

Fill both blanks to complete the preorder traversal visiting root, left, then right.

DSA Javascript

function preorder(node) {
  if (node == null) return;
  console.log(node[1]);
  preorder(node[2]);
  preorder(node.right);
}

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

A.value

B.left

C.right

D.parent

Attempts:

3 left

💡 Hint

Common Mistakes

Printing .left or .right instead of .value.

Visiting .right before .left.

First print the node's value, then recursively visit the left child, then the right child.

5fill in blank

hard

Fill all three blanks to complete preorder traversal: print root, visit left, then right.

DSA Javascript

function preorder(node) {
  if (node == null) return;
  console.log(node[1]);
  preorder(node[2]);
  preorder(node[3]);
}

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

A.value

B.left

C.right

D.parent

Attempts:

3 left

💡 Hint

Common Mistakes

Visiting right child before left child.

Printing .left or .right instead of .value.

Print the node's value, then visit left child, then right child for preorder traversal.