Fine calculation in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the fine amount based on days late.

LLD

fine = [1] * days_late

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

Adays_late

Btotal_fine

Crate_per_day

Dbase_fine

Attempts:

3 left

💡 Hint

Common Mistakes

Using days_late twice instead of rate_per_day

Using total_fine which is the result, not the rate

The fine is calculated by multiplying the rate per day by the number of days late.

2fill in blank

medium

Complete the code to check if a fine should be applied based on days late.

LLD

if [1] > 0:
    apply_fine = True

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

Adays_late

Btotal_fine

Crate_per_day

Dfine_amount

Attempts:

3 left

💡 Hint

Common Mistakes

Checking fine_amount instead of days_late

Using rate_per_day in the condition

We apply a fine only if the number of days late is greater than zero.

3fill in blank

hard

Fix the error in the code to correctly calculate the total fine with a maximum cap.

LLD

total_fine = min([1] * days_late, max_fine)

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

Atotal_fine

Brate_per_day

Cmax_fine

Ddays_late

Attempts:

3 left

💡 Hint

Common Mistakes

Using total_fine inside its own calculation

Using max_fine as multiplier instead of cap

The fine is calculated by multiplying the rate per day by days late, then capped by max_fine.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each user to their fine if late.

LLD

user_fines = {user: [1] * days for user, days in late_days.items() if days [2] 0}

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

Arate_per_day

B>

C==

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using equality instead of greater than in condition

Using wrong variable for multiplication

The fine is calculated by multiplying rate_per_day by days late, only for users with days late greater than zero.

5fill in blank

hard

Fill the blanks to filter users with fines above threshold and create a summary dictionary.

LLD

high_fines = {user: fine for user, fine in user_fines.items() if fine [1] threshold}
summary = {
    'count': len(high_fines),
    'max_fine': max(high_fines.values()) if high_fines else 0,
    'average_fine': sum(high_fines.values()) [2] len(high_fines) if high_fines else 0
}

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

A>

B//

C/

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using integer division '//' instead of '/' for average

Using '+' instead of division for average calculation

The code filters fines greater than the threshold, counts them, finds the max fine, and calculates the average by dividing the sum by count.

Practice

1.

What is the primary purpose of a fine calculation system in low-level design?

easy

A. To automatically compute charges for rule violations

B. To store user personal information securely

C. To manage user login and authentication

D. To generate reports on system performance

Solution

1. Step 1: Understand the system goal

   The fine calculation system is designed to handle rule violations and compute the corresponding charges automatically.

2. Step 2: Identify the main function

   Its main function is to calculate fines based on violation details and fixed rates.

3. Final Answer:

   To automatically compute charges for rule violations -> Option A

4. Quick Check:

   Fine calculation = automatic charge computation [OK]

Hint: Focus on the system's main task: charging fines [OK]

Common Mistakes:

• Confusing fine calculation with user management
• Thinking it handles authentication
• Assuming it generates performance reports

2.

Which of the following is the correct way to represent a fine rate for a violation type in a configuration file?

violation_fine_rates = {
    'speeding': 100,
    'parking': 50,
    'signal_jump': 150
}

easy

A. Using a boolean flag for each violation

B. Using a list of fine amounts only

C. Using a dictionary with violation types as keys and fine amounts as values

D. Using a string with violation names separated by commas

Solution

1. Step 1: Analyze the data structure

   The example shows a dictionary mapping violation names to their fine amounts, which is clear and easy to update.

2. Step 2: Compare with other options

   Lists or strings do not map violation types to amounts directly, and booleans cannot store fine values.

3. Final Answer:

   Using a dictionary with violation types as keys and fine amounts as values -> Option C

4. Quick Check:

   Dictionary maps violation to fine [OK]

Hint: Use key-value pairs for clear violation-to-fine mapping [OK]

Common Mistakes:

• Using lists without keys loses violation context
• Using strings cannot store amounts
• Booleans cannot represent fine values

3.

Given the following code snippet, what will be the total fine calculated?

violation_fine_rates = {'speeding': 100, 'parking': 50}
violations = ['speeding', 'parking', 'speeding']
total_fine = sum(violation_fine_rates[v] for v in violations)
print(total_fine)

medium

A. 150

B. 200

C. 300

D. 250

Solution

1. Step 1: Calculate fine for each violation

   Violations are 'speeding', 'parking', 'speeding'. Their fines are 100, 50, and 100 respectively.

2. Step 2: Sum all fines

   Total fine = 100 + 50 + 100 = 250.

3. Final Answer:

   250 -> Option D

4. Quick Check:

   100 + 50 + 100 = 250 [OK]

Hint: Add fines for each violation in the list [OK]

Common Mistakes:

• Counting each violation only once
• Adding fines incorrectly
• Ignoring repeated violations

4.

Identify the error in the following fine calculation code snippet:

violation_fine_rates = {'speeding': 100, 'parking': 50}
violations = ['speeding', 'parking', 'signal_jump']
total_fine = sum(violation_fine_rates[v] for v in violations)
print(total_fine)

medium

A. SyntaxError due to missing colon

B. KeyError occurs because 'signal_jump' is not in the rates dictionary

C. TypeError because sum cannot add strings

D. No error, code runs fine

Solution

1. Step 1: Check dictionary keys against violations

   'signal_jump' is not a key in violation_fine_rates, so accessing it causes a KeyError.

2. Step 2: Understand error type

   Attempting to access a missing key in a dictionary raises KeyError in Python.

3. Final Answer:

   KeyError occurs because 'signal_jump' is not in the rates dictionary -> Option B

4. Quick Check:

   Missing key access = KeyError [OK]

Hint: Check if all violation keys exist in the rates dictionary [OK]

Common Mistakes:

• Assuming missing keys return zero
• Confusing KeyError with SyntaxError
• Ignoring runtime errors

5.

You are designing a fine calculation system that must support multiple violation types, each with different fine rates and possible discounts for repeat offenses. Which design approach is best?

hard

A. Use a dictionary mapping violation types to base fines and add logic to apply discounts based on offense count

B. Store all fines as a single fixed value and ignore violation types

C. Calculate fines manually each time without storing rates

D. Use a list of fines without linking to violation types

Solution

1. Step 1: Identify need for flexible fine rates

   Different violation types require different base fines, so a mapping structure is needed.

2. Step 2: Incorporate discount logic

   Discounts for repeat offenses require additional logic applied on top of base fines.

3. Step 3: Choose design approach

   A dictionary for base fines plus discount logic is clear, scalable, and easy to update.

4. Final Answer:

   Use a dictionary mapping violation types to base fines and add logic to apply discounts based on offense count -> Option A

5. Quick Check:

   Dictionary + discount logic = scalable design [OK]

Hint: Map base fines and add discount logic for repeats [OK]

Common Mistakes:

• Ignoring violation types in fine calculation
• Hardcoding fines without flexibility
• Not handling repeat offense discounts