Lowest Common Ancestor in Binary Tree 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

if (root [1] null) return null;

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

A>

B!==

C<

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' or '!==' instead of '===' causes wrong logic.

Using '>' or '<' to compare with null is incorrect.

We check if root is exactly equal to null to stop recursion when we reach a leaf's child.

2fill in blank

medium

Complete the code to check if the current node matches either of the target nodes p or q.

DSA Javascript

if (root.val [1] p.val || root.val [1] q.val) return root;

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

A!==

B===

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' or '!==' instead of '===' causes wrong logic.

Using loose equality '==' can cause bugs.

We use strict equality '===' to check if the current node's value matches p or q.

3fill in blank

hard

Fix the error in the recursive calls to search left and right subtrees.

DSA Javascript

const left = lowestCommonAncestor(root.[1], p, q);
const right = lowestCommonAncestor(root.[2], p, q);

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

Aleft

Bright

CleftChild

DrightChild

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names like leftChild or rightChild.

Recursing on the same subtree twice.

We must recurse on root.left and root.right to search both subtrees.

4fill in blank

hard

Fill both blanks to return the correct ancestor based on left and right subtree results.

DSA Javascript

if (left [1] null && right [2] null) return root;

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 condition.

Using logical OR '||' instead of AND '&&' changes logic.

If both left and right are not null, root is the lowest common ancestor.

5fill in blank

hard

Fill the blanks to return the non-null subtree result or null.

DSA Javascript

return left [1] right ? left [2] right : null;

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

A!==

B||

C&&

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using '&&' instead of '||' changes the logic.

Using '===' instead of '!==' causes wrong checks.

Return left if left is not null; otherwise return right if right is not null; else null.