Why BST Over Plain Binary Tree in DSA Typescript - Test Your Knowledge

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a value into a Binary Search Tree (BST).

DSA Typescript

function insert(node: TreeNode | null, value: number): TreeNode {
  if (node === null) {
    return new TreeNode(value);
  }
  if (value [1] node.value) {
    node.left = insert(node.left, value);
  } else {
    node.right = insert(node.right, value);
  }
  return node;
}

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

A<

B>

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' causes wrong placement.

In a BST, values less than the current node go to the left subtree.

2fill in blank

medium

Complete the code to search for a value in a BST.

DSA Typescript

function search(node: TreeNode | null, value: number): boolean {
  if (node === null) return false;
  if (value === node.value) return true;
  if (value [1] node.value) {
    return search(node.left, value);
  } else {
    return search(node.right, value);
  }
}

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

A>

B==

C<

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing '<' and '>' leads to wrong search path.

To search in BST, if value is less than node's value, search left subtree.

3fill in blank

hard

Fix the error in the code that checks if a tree is a BST.

DSA Typescript

function isBST(node: TreeNode | null, min: number | null = null, max: number | null = null): boolean {
  if (node === null) return true;
  if ((min !== null && node.value [1]= min) || (max !== null && node.value [2]= max)) {
    return false;
  }
  return isBST(node.left, min, node.value) && isBST(node.right, node.value, max);
}

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

A<

B<=

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '>' alone misses equal values violating BST rules.

Use '<=' and '>=' to ensure no duplicates violate BST property.

4fill in blank

hard

Fill both blanks to create a function that finds the minimum value in a BST.

DSA Typescript

function findMin(node: TreeNode | null): number | null {
  if (node === null) return null;
  while (node.[1] !== null) {
    node = node.[2];
  }
  return node.value;
}

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

Aleft

Bright

Cparent

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'right' instead of 'left' finds maximum, not minimum.

The minimum value in a BST is found by going left until no more left child exists.

5fill in blank

hard

Fill all three blanks to implement in-order traversal of a BST that collects values in an array.

DSA Typescript

function inorderTraversal(node: TreeNode | null, result: number[] = []): number[] {
  if (node !== null) {
    inorderTraversal(node.[1], result);
    result.push(node.[2]);
    inorderTraversal(node.[3], result);
  }
  return result;
}

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

Aleft

Bvalue

Cright

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing order leads to incorrect traversal sequence.

In-order traversal visits left subtree, node value, then right subtree.