Tree traversals (inorder, preorder, postorder) in Data Structures Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print the root node first in a preorder traversal.

Data Structures Theory

def preorder(node):
    if node is None:
        return
    print(node.value)
    preorder(node.[1])
    preorder(node.right)

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

Aleft

Bchild

Cparent

Dright

Attempts:

3 left

💡 Hint

Common Mistakes

Calling preorder on the right child first.

Trying to access a non-existent attribute like 'parent'.

In preorder traversal, we visit the root node first, then the left subtree, followed by the right subtree. So, the first recursive call should be on the left child.

2fill in blank

medium

Complete the code to traverse the left subtree first in an inorder traversal.

Data Structures Theory

def inorder(node):
    if node is None:
        return
    inorder(node.[1])
    print(node.value)
    inorder(node.right)

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

Aparent

Bleft

Cright

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Visiting the right subtree before the left.

Printing the node value before traversing the left subtree.

In inorder traversal, we visit the left subtree first, then the root node, and finally the right subtree. So, the first recursive call should be on the left child.

3fill in blank

hard

Fix the error in the postorder traversal code to visit the right subtree last.

Data Structures Theory

def postorder(node):
    if node is None:
        return
    postorder(node.left)
    postorder(node.[1])
    print(node.value)

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

Aleft

Bparent

Cright

Dchild

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the node value before visiting the right subtree.

Visiting the right subtree before the left.

In postorder traversal, we visit the left subtree, then the right subtree, and finally the root node. The print statement should come after both recursive calls. The blank should be filled with 'right' to visit the right subtree last.

4fill in blank

hard

Fill both blanks to complete the inorder traversal that visits left subtree, root, then right subtree.

Data Structures Theory

def inorder(node):
    if node is None:
        return
    inorder(node.[1])
    print(node.[2])
    inorder(node.right)

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

Aleft

Bvalue

Cright

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the node object instead of its value.

Visiting the right child before printing the node's value.

In inorder traversal, we first visit the left child, then print the node's value, and finally visit the right child. So, the first blank is 'left' and the second blank is 'value'.

5fill in blank

hard

Fill all three blanks to complete the preorder traversal visiting root, left subtree, then right subtree.

Data Structures Theory

def preorder(node):
    if node is None:
        return
    print(node.[1])
    preorder(node.[2])
    preorder(node.[3])

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

Avalue

Bleft

Cright

Dparent

Attempts:

3 left

💡 Hint

Common Mistakes

Printing the node after traversing children.

Swapping left and right child traversal order.

In preorder traversal, we print the root node's value first, then recursively traverse the left subtree, followed by the right subtree. So the blanks are 'value', 'left', and 'right' respectively.