BST Delete Operation in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Typescript

if (root === [1]) {
    return root;
}

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

Aundefined

B0

Cnull

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined instead of null causes the check to fail.

Using 0 or false is incorrect because nodes are objects, not booleans or numbers.

We check if the root is null to know if the tree or subtree is empty, so we return it as is.

2fill in blank

medium

Complete the code to move left or right in the BST based on the key value.

DSA Typescript

if (key < root.val) {
    root.left = deleteNode(root.left, [1]);
} else if (key > root.val) {
    root.right = deleteNode(root.right, key);
}

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

Akey

Broot.val

Croot.left

Droot.right

Attempts:

3 left

💡 Hint

Common Mistakes

Passing root.val instead of key causes wrong recursion.

Passing root.left or root.right is incorrect because those are nodes, not keys.

We pass the key down the tree to find the node to delete.

3fill in blank

hard

Fix the error in finding the minimum value node in the right subtree.

DSA Typescript

let minNode = root.right;
while (minNode.[1] !== null) {
    minNode = minNode.left;
}

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

Aright

Bleft

Cval

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Checking minNode.right in the while condition causes infinite loop or wrong node.

Using minNode.val or minNode.parent is incorrect for traversal.

To find the minimum node in the right subtree, we keep going left until there is no left child. The loop condition checks if minNode.left is not null to continue.

4fill in blank

hard

Fill both blanks to replace the node's value with the minimum node's value and delete the minimum node.

DSA Typescript

root.val = minNode.[1];
root.right = deleteNode(root.right, [2]);

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

Aval

Bleft

CminNode.val

DminNode.left

Attempts:

3 left

💡 Hint

Common Mistakes

Using minNode.left or minNode.right instead of minNode.val causes errors.

Passing minNode.left instead of minNode.val to deleteNode causes wrong deletion.

We copy the minimum node's value to the current node, then delete the minimum node by passing its value to the delete function.

5fill in blank

hard

Fill all three blanks to handle the case when the node to delete has only one child.

DSA Typescript

if (root.left === null) {
    return root.[1];
} else if (root.right === null) {
    return root.[2];
}

// Node with two children handled later

return [3];

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

Aleft

Bright

Croot

DdeleteNode(root.left, key)

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping left and right in returns causes wrong tree structure.

Returning deleteNode call instead of root in last blank causes infinite recursion.

If the node has no left child, we return its right child to replace it. If no right child, we return its left child. Otherwise, we return the current root after handling two children case.