Two Sum in BST in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Javascript

if (root [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 ===

Using assignment = instead of comparison ===

We check if root is exactly equal to null to stop recursion.

2fill in blank

medium

Complete the code to add a value to the set.

DSA Javascript

set.[1](root.val);

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Apush

Binsert

Cappend

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using push() which is for arrays

Using insert() which is not a Set method

JavaScript Set uses add() to insert values.

3fill in blank

hard

Fix the error in checking if the complement exists in the set.

DSA Javascript

if (set.[1](target - root.val)) return true;

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Ahas

Bincludes

Cfind

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using contains() which is not a Set method

Using includes() which is for arrays

Set uses has() method to check for presence of an element.

4fill in blank

hard

Fill both blanks to complete the recursive calls for left and right subtrees.

DSA Javascript

return dfs(root.[1], set, target) || dfs(root.[2], set, target);

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Aleft

Bright

Cchild

Dnode

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect property names like child or node

Calling dfs on the same child twice

We recursively call dfs on left and right children of the node.

5fill in blank

hard

Fill all three blanks to complete the main function that uses DFS and a set.

DSA Javascript

var findTarget = function(root, target) {
  const set = new Set();
  function dfs(node, set, target) {
    if (node [1] null) return false;
    if (set.[2](target - node.val)) return true;
    set.[3](node.val);
    return dfs(node.left, set, target) || dfs(node.right, set, target);
  }
  return dfs(root, set, target);
};

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

A===

Bhas

Cadd

D!==

Attempts:

3 left

💡 Hint

Common Mistakes

Using != instead of === for null check

Using contains instead of has for set

Using push instead of add for set

Check if node is null with ===, check set with has(), add node.val with add().