Tree Traversal Postorder Left Right Root in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the postorder traversal by visiting the left child first.

DSA Typescript

function postorder(node: TreeNode | null): void {
  if (node === null) return;
  postorder(node.[1]);
  // continue traversal
}

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

Aleft

Bright

Cparent

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'right' instead of 'left' for the first recursive call.

Trying to access 'parent' which is not part of traversal here.

In postorder traversal, we visit the left child first before right and root.

2fill in blank

medium

Complete the code to visit the right child after the left child in postorder traversal.

DSA Typescript

function postorder(node: TreeNode | null): void {
  if (node === null) return;
  postorder(node.left);
  postorder(node.[1]);
  // continue traversal
}

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

Aparent

Broot

Cright

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'parent' or 'root' instead of 'right'.

Skipping the right child call.

After visiting the left child, postorder traversal visits the right child.

3fill in blank

hard

Fix the error in the code to correctly print the root node's value after visiting children.

DSA Typescript

function postorder(node: TreeNode | null): void {
  if (node === null) return;
  postorder(node.left);
  postorder(node.right);
  console.log(node.[1]);
}

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

Aparent

Bleft

Cright

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Printing node.left or node.right instead of node.value.

Trying to print node.parent which may not exist.

We print the node's value after visiting left and right children in postorder.

4fill in blank

hard

Fill both blanks to create a postorder traversal that collects node values in an array.

DSA Typescript

function postorderCollect(node: TreeNode | null, result: number[]): void {
  if (node === null) return;
  postorderCollect(node.[1], result);
  postorderCollect(node.[2], result);
  result.push(node.value);
}

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

Aleft

Bright

Cparent

Droot

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping left and right children.

Using 'parent' or 'root' which are not children.

Postorder visits left child first, then right child, then root.

5fill in blank

hard

Fill all three blanks to create a postorder traversal that returns an array of node values.

DSA Typescript

function postorderReturn(node: TreeNode | null): number[] {
  if (node === null) return [];
  const leftVals = postorderReturn(node.[1]);
  const rightVals = postorderReturn(node.[2]);
  return [...leftVals, ...rightVals, node.[3]];
}

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

Aleft

Bright

Cvalue

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Returning node.left or node.right instead of node.value.

Swapping left and right children.

Postorder traversal collects left subtree values, then right subtree values, then the current node's value.