Path Sum Root to Leaf in Binary Tree in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Typescript

if (node [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 logic.

Using '>' or '<' operators for null check.

We check if the node is exactly equal to null to stop recursion.

2fill in blank

medium

Complete the code to check if the current node is a leaf node.

DSA Typescript

if (node.left === null && node.right [1] null) return sum + node.val === targetSum;

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 leaf detection.

Checking only one child for null.

A leaf node has both left and right children as null.

3fill in blank

hard

Fix the error in the recursive call to check left subtree.

DSA Typescript

return helper(node.left, sum [1] node.val, targetSum) || helper(node.right, sum + node.val, targetSum);

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

A/

B-

C+

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-' causes decreasing sum incorrectly.

Using '*' or '/' causes wrong calculations.

We add the current node's value to the sum when going down the tree.

4fill in blank

hard

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

DSA Typescript

function hasPathSum([1]: TreeNode | null, targetSum: number): boolean {
  return helper([2], 0, targetSum);
}

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

Anode

Broot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'node' in parameter but calling helper with 'root'.

Mismatch between parameter name and argument.

The function parameter is named 'root' and the helper is called with 'root'.

5fill in blank

hard

Fill all three blanks to complete the helper function for path sum check.

DSA Typescript

function helper(node: TreeNode | null, sum: number, targetSum: number): boolean {
  if (node === null) return [1];
  if (node.left === null && node.right === null) return sum + node.val === [2];
  return helper(node.left, sum [3] node.val, targetSum) || helper(node.right, sum + node.val, targetSum);
}

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

Afalse

BtargetSum

C+

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Returning true when node is null causes wrong results.

Comparing sum instead of sum + node.val to targetSum.

Using wrong operator instead of '+' in recursion.

Return false if node is null, compare sum + node.val to targetSum, and add node.val to sum in recursion.