Level-order traversal (BFS) in Data Structures Theory - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue with the root node for level-order traversal.

Data Structures Theory

queue = [[1]]

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ANone

B[]

Croot

Dstack

Attempts:

3 left

💡 Hint

Common Mistakes

Using an empty list instead of the root node.

Initializing with None instead of the root.

Using a stack instead of a queue.

The level-order traversal starts by adding the root node to the queue.

2fill in blank

medium

Complete the code to remove the first node from the queue during traversal.

Data Structures Theory

current_node = queue.[1]

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Apop

Bpop(0)

Cdequeue

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() which removes the last element.

Using remove() which requires a value, not an index.

Using dequeue() which is not a list method.

In level-order traversal, nodes are removed from the front of the queue using pop(0).

3fill in blank

hard

Fix the error in the code to add the left child to the queue if it exists.

Data Structures Theory

if current_node.[1] is not None:
    queue.append(current_node.left)

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AleftNode

Bchild

Cleft_child

Dleft

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect attribute names like 'child' or 'left_child'.

Using camelCase instead of snake_case.

The left child of a node is accessed by the attribute 'left'.

4fill in blank

hard

Fill both blanks to add the right child to the queue if it exists.

Data Structures Theory

if current_node.[1] is not None:
    queue.[2](current_node.right)

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Aright

Bappend

Cadd

Dright_child

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'add' instead of 'append' for lists.

Using incorrect attribute names like 'right_child'.

The right child is accessed by 'right' and added to the queue using 'append'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps each node to its level in the tree during BFS.

Data Structures Theory

levels = { [1]: [2] for [3] in nodes }

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Anode.value

Blevel

Cnode

Attempts:

3 left

💡 Hint

Common Mistakes

Using node.value as key instead of node.

Mixing variable names inconsistently.

This comprehension creates a dictionary where each node maps to its level. 'node' is the variable, 'level' is the value, and 'node.value' would be incorrect here.