Order state machine in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the initial state of the order.

LLD

class OrderStateMachine:
    def __init__(self):
        self.state = "[1]"

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

ACancelled

BShipped

CCreated

DDelivered

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'Shipped' or 'Delivered' as the initial state.

Using 'Cancelled' as the starting state.

The initial state of an order is usually 'Created' when it is first made.

2fill in blank

medium

Complete the code to transition the order from 'Created' to the next state.

LLD

def advance_order(self):
    if self.state == "Created":
        self.state = "[1]"

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ADelivered

BShipped

CCancelled

DReturned

Attempts:

3 left

💡 Hint

Common Mistakes

Skipping 'Shipped' and going directly to 'Delivered'.

Using 'Cancelled' as the next state after 'Created'.

After creation, the order moves to 'Shipped' when it is sent out.

3fill in blank

hard

Fix the error in the code that checks if the order can be cancelled only when it is in 'Created' state.

LLD

def cancel_order(self):
    if self.state == "[1]":
        self.state = "Cancelled"

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

ACreated

BDelivered

CShipped

DReturned

Attempts:

3 left

💡 Hint

Common Mistakes

Allowing cancellation after the order is shipped or delivered.

Using 'Shipped' or 'Delivered' as the cancellable state.

An order can only be cancelled if it is still in the 'Created' state before shipping.

4fill in blank

hard

Fill both blanks to complete the method that returns True if the order is in a final state.

LLD

def is_final_state(self):
    return self.state == "[1]" or self.state == "[2]"

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

ACancelled

BCreated

CDelivered

DShipped

Attempts:

3 left

💡 Hint

Common Mistakes

Including 'Created' or 'Shipped' as final states.

Missing one of the final states in the check.

The final states of an order are 'Cancelled' and 'Delivered' because no further transitions occur after these.

5fill in blank

hard

Fill all three blanks to complete the transition method that moves the order from 'Shipped' to 'Delivered' or 'Returned'.

LLD

def update_after_shipping(self, returned):
    if self.state == "[1]":
        if returned:
            self.state = "[2]"
        else:
            self.state = "[3]"

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

ACreated

BReturned

CDelivered

DShipped

Attempts:

3 left

💡 Hint

Common Mistakes

Checking wrong initial state before update.

Swapping 'Delivered' and 'Returned' states.

The order must be in 'Shipped' state to update. If returned is True, state changes to 'Returned', else to 'Delivered'.