Validate if Tree is BST in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the current node is null.

DSA Javascript

function isBST(node) {
  if (node [1] null) {
    return true;
  }
  // further checks
}

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

A||

B===

C&&

D!==

Attempts:

3 left

💡 Hint

Common Mistakes

Using != instead of === causes incorrect base case handling.

Using logical operators instead of comparison.

We check if the node is exactly equal to null to handle the base case of recursion.

2fill in blank

medium

Complete the code to check if the left child's value is less than the current node's value.

DSA Javascript

if (node.left !== null && node.left.val [1] node.val) {
  return false;
}

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 validation.

Using equality check instead of comparison.

For a BST, left child's value must be less than the current node's value. If it is greater or equal, return false.

3fill in blank

hard

Fix the error in the recursive call to validate the right subtree with updated min value.

DSA Javascript

return isBST(node.left, min, node.val) && isBST(node.right, [1], max);

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

Anode.val

Bmin

Cmax

Dnode.left.val

Attempts:

3 left

💡 Hint

Common Mistakes

Passing min instead of node.val causes incorrect range checks.

Passing max instead of min for right subtree.

For the right subtree, the minimum allowed value is the current node's value.

4fill in blank

hard

Fill both blanks to complete the function signature and initial call for BST validation.

DSA Javascript

function isBST(node, [1] = -Infinity, [2] = Infinity) {
  if (node === null) return true;
  // validation logic
}

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

Amin

Bmax

Cvalue

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names causes confusion.

Swapping min and max values.

The function uses min and max to keep track of valid value ranges for nodes.

5fill in blank

hard

Fill all four blanks to complete the BST validation condition inside the function.

DSA Javascript

if (node.val [1] [2] || node.val [3] [4]) {
  return false;
}

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

A<=

B>=

Cmin

Dmax

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators.

Swapping min and max in conditions.

The node's value must be greater than min and less than max to be valid in BST.