Tree Traversal Inorder Left Root Right in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to visit the left subtree first in inorder traversal.

DSA Typescript

function inorder(node: TreeNode | null): void {
  if (node === null) return;
  inorder(node[1]);
  console.log(node.val);
  inorder(node.right);
}

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

A.left

B.val

C.parent

D.right

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.right instead of node.left for the first recursive call.

Trying to access node.val instead of a child node.

In inorder traversal, we first visit the left child, so we call inorder(node.left).

2fill in blank

medium

Complete the code to print the root node value in inorder traversal.

DSA Typescript

function inorder(node: TreeNode | null): void {
  if (node === null) return;
  inorder(node.left);
  console.log(node[1]);
  inorder(node.right);
}

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

A.parent

B.right

C.left

D.val

Attempts:

3 left

💡 Hint

Common Mistakes

Printing node.left or node.right instead of node.val.

Trying to print node.parent which may not exist.

In inorder traversal, after visiting left subtree, we print the root node's value using node.val.

3fill in blank

hard

Fix the error in the inorder traversal recursive call for the right subtree.

DSA Typescript

function inorder(node: TreeNode | null): void {
  if (node === null) return;
  inorder(node.left);
  console.log(node.val);
  inorder(node[1]);
}

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

A.parent

B.left

C.right

D.val

Attempts:

3 left

💡 Hint

Common Mistakes

Calling inorder(node.left) again instead of node.right.

Trying to call inorder(node.val) which is a value, not a node.

The right subtree is visited by calling inorder(node.right) in inorder traversal.

4fill in blank

hard

Fill both blanks to complete the inorder traversal that collects values in an array.

DSA Typescript

function inorder(node: TreeNode | null, result: number[]): void {
  if (node === null) return;
  inorder(node[1], result);
  result.push(node[2]);
  inorder(node.right, result);
}

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

A.left

B.val

C.right

D.parent

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.right in the first recursive call instead of node.left.

Pushing node.right or node.left instead of node.val.

We first recurse on the left child (node.left), then push the root value (node.val) to the result array.

5fill in blank

hard

Fill all three blanks to complete inorder traversal that returns an array of values.

DSA Typescript

function inorder(node: TreeNode | null): number[] {
  if (node === null) return [];
  const left = inorder(node[1]);
  const right = inorder(node[2]);
  return [...left, node[3], ...right];
}

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

A.left

B.right

C.val

D.parent

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping left and right children in recursive calls.

Using node.parent or node.val in recursive calls instead of child nodes.

Returning node instead of node.val in the combined array.

We recursively get left subtree values with node.left, right subtree values with node.right, and combine them with the root value node.val in the middle.