Check if Two Trees are Symmetric in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if two nodes are both null.

DSA Javascript

if (node1 === null && node2 [1] null) return true;

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 logic.

Using !== between node2 and null instead of ===.

We check if both nodes are null using the strict equality operator (===).

2fill in blank

medium

Complete the code to check if one node is null and the other is not.

DSA Javascript

if (node1 === null || node2 [1] null) 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 detection.

Using logical operators instead of comparison operators.

We check if one node is null and the other is not using !==.

3fill in blank

hard

Fix the error in comparing node values for symmetry.

DSA Javascript

if (node1.val [1] node2.val) return false;

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

A!==

B===

C<=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using === causes wrong logic because it returns false when values differ.

Using < or > is incorrect for equality check.

If the values are not equal (!==), the trees are not symmetric.

4fill in blank

hard

Fill both blanks to recursively check left and right subtrees for symmetry.

DSA Javascript

return isSymmetricHelper(node1.[1], node2.[2]) && isSymmetricHelper(node1.[2], node2.[1]);

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

Aleft

Bright

Cval

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'val' or 'parent' instead of 'left' or 'right' causes errors.

Swapping left and right incorrectly breaks symmetry check.

We compare node1's left with node2's right and node1's right with node2's left.

5fill in blank

hard

Fill all three blanks to define the main function calling the helper.

DSA Javascript

function isSymmetric(root) {
  if (root === null) return true;
  return isSymmetricHelper(root.[1], root.[2]);
}

function isSymmetricHelper(node1, node2) {
  if (node1 === null && node2 === null) return true;
  if (node1 === null || node2 === null) return false;
  if (node1.val [3] node2.val) return false;
  return isSymmetricHelper(node1.left, node2.right) && isSymmetricHelper(node1.right, node2.left);
}

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

Aleft

Bright

C!==

D===

Attempts:

3 left

💡 Hint

Common Mistakes

Using === instead of !== for value comparison.

Swapping left and right in the main function call.

The main function compares root.left and root.right, and the helper checks if values differ using !==.