Room type hierarchy in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the base class for all room types.

LLD

class [1]:
    def __init__(self, room_number):
        self.room_number = room_number

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

ARoom

BRoomType

CBaseRoom

DRoomBase

Attempts:

3 left

💡 Hint

Common Mistakes

Using plural names like Rooms

Using unrelated names like Building

The base class for all room types is commonly named Room to represent a generic room.

2fill in blank

medium

Complete the code to define a subclass for a conference room inheriting from the base room.

LLD

class ConferenceRoom([1]):
    def __init__(self, room_number, capacity):
        super().__init__(room_number)
        self.capacity = capacity

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

ARoom

BRoomType

CBaseRoom

DBuilding

Attempts:

3 left

💡 Hint

Common Mistakes

Inheriting from unrelated classes

Forgetting to call super().__init__

The subclass ConferenceRoom inherits from the base class Room.

3fill in blank

hard

Fix the error in the method overriding to return the room type name.

LLD

class MeetingRoom(Room):
    def get_type(self):
        return [1]

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

Aself.MeetingRoom

BMeetingRoom

C'MeetingRoom'

Dget_type

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the class name without quotes

Returning a method name instead of a string

The method should return the string 'MeetingRoom' to indicate the room type.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension mapping room numbers to their types for rooms with capacity over 10.

LLD

room_types = {room.room_number: room.get_type() for room in rooms if room.[1] > [2]

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

Acapacity

Bsize

C10

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong attribute names

Using incorrect threshold values

The comprehension filters rooms with capacity greater than 10.

5fill in blank

hard

Fill all three blanks to create a list comprehension of room numbers for rooms that are either ConferenceRoom or MeetingRoom.

LLD

selected_rooms = [room.[1] for room in rooms if isinstance(room, [2]) or isinstance(room, [3])]

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

Aroom_number

BConferenceRoom

CMeetingRoom

DRoom

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong attribute names

Checking against the base Room class instead of subclasses

The list comprehension collects room_number for rooms that are instances of ConferenceRoom or MeetingRoom.

Practice

1. What is the main purpose of using a Room type hierarchy in system design?

easy

A. To randomly assign room types without any structure

B. To organize rooms by shared and unique features for easier maintenance

C. To store all room data in a single flat list without categories

D. To duplicate room properties in every class separately

Solution

1. Step 1: Understand the concept of hierarchy

   A hierarchy groups items by common traits, making management simpler.

2. Step 2: Apply to room types

   Using a base class for shared features and subclasses for specifics avoids duplication and eases updates.

3. Final Answer:

   To organize rooms by shared and unique features for easier maintenance -> Option B

4. Quick Check:

   Hierarchy = Organize by features [OK]

Hint: Think: shared features go in base, unique in subclasses [OK]

Common Mistakes:

• Confusing hierarchy with flat lists
• Duplicating properties in every room class
• Ignoring shared features in base class

2. Which of the following is the correct way to define a base class Room with a subclass ConferenceRoom in a typical object-oriented design?

easy

A. class Room {}; class ConferenceRoom extends Room {}

B. class Room; class ConferenceRoom inherits Room

C. class Room() {}; class ConferenceRoom() inherits Room()

D. class Room {}; class ConferenceRoom inherits Room {}

Solution

1. Step 1: Identify correct syntax for inheritance

   In many modern languages, extends is used to inherit from a base class.

2. Step 2: Check each option

   class Room {}; class ConferenceRoom extends Room {} uses correct syntax: class ConferenceRoom extends Room {}. Others use incorrect or incomplete syntax.

3. Final Answer:

   class Room {}; class ConferenceRoom extends Room {} -> Option A

4. Quick Check:

   Inheritance syntax = extends [OK]

Hint: Remember: subclass extends base class in OOP [OK]

Common Mistakes:

• Using 'inherits' instead of 'extends'
• Missing curly braces for class body
• Incorrect parentheses in class declaration

3. Given this Python-like pseudocode for room types:

class Room:
    def __init__(self, name):
        self.name = name

class Bedroom(Room):
    def __init__(self, name, bed_size):
        super().__init__(name)
        self.bed_size = bed_size

room = Bedroom('Master', 'King')
print(room.name, room.bed_size)

What will be the output?

medium

A. Error: missing argument

B. Bedroom King

C. Master None

D. Master King

Solution

1. Step 1: Trace object creation

   Creating Bedroom('Master', 'King') calls Bedroom's constructor, which calls Room's constructor with 'Master'.

2. Step 2: Check printed attributes

   room.name is 'Master' from Room; room.bed_size is 'King' from Bedroom.

3. Final Answer:

   Master King -> Option D

4. Quick Check:

   Subclass calls base, attributes set correctly [OK]

Hint: Remember: super() sets base class attributes [OK]

Common Mistakes:

• Assuming subclass overwrites base attributes
• Forgetting to call super().__init__
• Confusing attribute names

4. Consider this code snippet for a room hierarchy:

class Room:
    def __init__(self, name):
        self.name = name

class MeetingRoom(Room):
    def __init__(self, name, capacity):
        self.capacity = capacity

room = MeetingRoom('Boardroom', 20)
print(room.name, room.capacity)

What is the issue here?

medium

A. capacity attribute is not set correctly

B. Syntax error in class definition

C. Missing call to base class constructor causes room.name to be undefined

D. No issue; code runs fine

Solution

1. Step 1: Check constructor chaining

   MeetingRoom's constructor sets capacity but does not call super().__init__(name), so name is not set.

2. Step 2: Understand effect on attributes

   Without base constructor call, room.name is missing, causing error or undefined behavior.

3. Final Answer:

   Missing call to base class constructor causes room.name to be undefined -> Option C

4. Quick Check:

   Always call base __init__ in subclass [OK]

Hint: Call super().__init__ to set base attributes [OK]

Common Mistakes:

• Assuming base constructor runs automatically
• Ignoring missing attributes in subclass
• Confusing syntax errors with logic errors

5. You need to design a room type hierarchy for a hotel system that includes Room, Bedroom, ConferenceRoom, and Suite. Suites can have multiple bedrooms and a living area. Which design approach best models this?

hard

A. Make Suite inherit from Room and include a list of Bedroom objects plus living area

B. Make Suite inherit from Bedroom and add living area attributes

C. Make Suite a separate class unrelated to Room hierarchy

D. Make Bedroom inherit from Suite to reuse features

Solution

1. Step 1: Analyze relationships

   Suite is a special Room that contains multiple Bedrooms and a living area, so it should inherit from Room.

2. Step 2: Model composition

   Suite should have a list of Bedroom objects (composition) to represent multiple bedrooms, plus its own living area attributes.

3. Final Answer:

   Make Suite inherit from Room and include a list of Bedroom objects plus living area -> Option A

4. Quick Check:

   Use inheritance + composition for complex types [OK]

Hint: Use composition for multiple rooms inside Suite [OK]

Common Mistakes:

• Using inheritance to model 'has-many' relationships
• Ignoring composition for complex room types
• Making unrelated classes inherit incorrectly