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

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if both nodes are null, which means symmetry at this point.

DSA Typescript

if (root1 === null && root2 [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 symmetry check.

Using '>' or '<' operators here is incorrect.

Both nodes being null means they are symmetric here, so we check if root2 is equal to null.

2fill in blank

medium

Complete the code to check if either node is null, which means trees are not symmetric.

DSA Typescript

if (root1 === null || root2 [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 symmetry detection.

Using '>' or '<' operators here is incorrect.

If one node is null and the other is not, trees are not symmetric, so we check if root2 is not null.

3fill in blank

hard

Fix the error in comparing the values of the two nodes to check symmetry.

DSA Typescript

if (root1.val [1] root2.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 symmetry detection.

Using '>' or '<' operators here is incorrect.

If the values are not equal, the trees are not symmetric, so we check if root1.val is not equal to root2.val.

4fill in blank

hard

Fill both blanks to recursively check the left subtree of root1 with the right subtree of root2 and vice versa.

DSA Typescript

return isSymmetricHelper(root1.[1], root2.[2]) && isSymmetricHelper(root1.right, root2.left);

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

Aleft

Bright

Croot

Dval

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping left and right incorrectly.

Using 'val' or 'root' instead of child nodes.

To check symmetry, compare root1's left with root2's right and root1's right with root2's left.

5fill in blank

hard

Fill all three blanks to define the helper function signature and call it from the main function.

DSA Typescript

function [1](root1: TreeNode | null, root2: TreeNode | null): boolean {
  // helper logic here
}

function [2](root: TreeNode | null): boolean {
  if (root === null) return true;
  return [3](root.left, root.right);
}

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

AisSymmetricHelper

BisSymmetric

DcheckSymmetry

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up function names.

Not calling the helper function from main.

The helper function is named isSymmetricHelper, the main function is isSymmetric, and the main function calls isSymmetricHelper.