Path Sum Root to Leaf 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 (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 '!=' or '!==' which changes the logic.

Using '>' or '<' which are not suitable for null checks.

We check if the node is exactly equal to null to know if we reached a leaf's child.

2fill in blank

medium

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

DSA Javascript

if (node.left === null && node.[1] === null) {

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

Aright

Bvalue

Cparent

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Checking 'parent' or 'value' instead of 'right'.

Using 'root' which is not a property of the node.

A leaf node has no left or right children, so both must be null.

3fill in blank

hard

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

DSA Javascript

return hasPathSum(node.left, sum [1] node.value) || hasPathSum(node.right, sum - node.value);

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

A*

B+

C-

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+' instead of '-' which leads to wrong sum calculation.

Using '*' or '/' which are not relevant here.

We subtract the current node's value from sum to check the remaining sum in the subtree.

4fill in blank

hard

Fill both blanks to complete the base case for leaf node sum check.

DSA Javascript

if (node.left === null && node.right === null) {
  return sum [1] node.value;
}

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

A>

B===

C!==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' or '!==', which would invert the logic.

Using '>' or '<' which are not correct for equality check.

At a leaf node, check if the remaining sum equals the node's value.

5fill in blank

hard

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

DSA Javascript

function hasPathSum(node, sum) {
  if (node [1] null) return false;
  if (node.left === null && node.right === null) {
    return sum [2] node.value;
  }
  return hasPathSum(node.left, sum [3] node.value) || hasPathSum(node.right, sum - node.value);
}

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

A===

B-

C!==

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using '===' to check node null which reverses logic.

Using '+' instead of '-' in recursive calls.

Using '!=' instead of '===' for sum comparison.

Check node not null with '!==', compare sum and node.value with '===', and subtract node.value from sum in recursion.