Split strategies (equal, exact, percentage) in LLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Equal Split Strategy

In a system that splits a bill equally among 4 users, each user pays the same amount. If the total bill is $120, how much does each user pay?

A $20

B $40

C $25

D $30

💡 Hint

Divide the total amount by the number of users.

Equal split means dividing the total amount equally among all users. $120 divided by 4 users equals $30 each.

❓ Architecture

intermediate

Designing Exact Split Strategy Component

You need to design a component that handles exact split strategy where each user pays a specified amount. Which of the following is the best way to validate the input amounts before processing?

A Check if the sum of all user amounts equals the total bill amount.

B Check if each user amount is greater than zero.

C Check if the number of users matches the number of amounts provided.

D Check if the total bill amount is divisible by the number of users.

💡 Hint

The total of all exact amounts must match the bill.

In exact split, the sum of all user amounts must equal the total bill to ensure correctness.

❓ scaling

advanced

Scaling Percentage Split Strategy for Large User Base

A system uses percentage split strategy to divide a bill among 10,000 users. Each user has a percentage share. What is the main challenge in scaling this system?

A Storing each user's percentage in a separate database table.

B Ensuring the sum of all percentages equals 100% to avoid rounding errors.

C Allowing users to change their percentage share in real-time without locking.

D Calculating each user's share by multiplying total bill with their percentage.

💡 Hint

Think about accuracy and consistency when dealing with many users.

With many users, rounding errors can accumulate if percentages do not sum exactly to 100%, causing billing mismatches.

❓ tradeoff

advanced

Tradeoffs Between Split Strategies

Which of the following is a key tradeoff when choosing between equal, exact, and percentage split strategies in a payment system?

A Equal split is simplest but less flexible; exact split is precise but requires more input; percentage split balances flexibility and complexity.

B Exact split is simplest and fastest; equal split requires complex calculations; percentage split is rarely used.

C Percentage split is always the most accurate; equal and exact splits cause errors.

D All split strategies have the same complexity and accuracy.

💡 Hint

Consider user input complexity and flexibility.

Equal split is easy but inflexible. Exact split needs detailed input. Percentage split offers flexibility but requires careful validation.

❓ estimation

expert

Estimating System Capacity for Percentage Split Strategy

You are designing a system to handle percentage split payments for up to 1 million users per bill. Each user’s percentage share must be stored and processed. Which factor most impacts the system’s capacity and performance?

A The UI responsiveness when displaying the total bill amount.

B The database schema used to store user profiles unrelated to payments.

C The memory required to store all user percentage shares and the CPU time to calculate each share.

D The network bandwidth to send the total bill amount to all users.

💡 Hint

Think about data size and computation for large user counts.

Storing and processing 1 million percentage shares requires significant memory and CPU resources, impacting capacity and performance.

Practice

1. Which split strategy divides an amount so that everyone pays the same share regardless of individual preferences?

easy

A. Equal split

B. Exact split

C. Percentage split

D. Random split

Solution

1. Step 1: Understand the definition of equal split

   Equal split means dividing the total amount evenly among all participants.

2. Step 2: Compare with other splits

   Exact split assigns specific amounts, percentage split assigns based on percent, random split is not a standard method.

3. Final Answer:

   Equal split -> Option A

4. Quick Check:

   Equal split = same share for all [OK]

Hint: Equal split means everyone pays the same amount [OK]

Common Mistakes:

• Confusing exact split with equal split
• Thinking percentage split always equals equal split
• Assuming random split is a valid standard method

2. Which of the following is the correct syntax to represent a percentage split of 40% for user A and 60% for user B in a system design context?

easy

A. {'A': '40%', 'B': '60%'}

B. {'A': 40, 'B': 60}

C. {'A': 0.4, 'B': 0.6}

D. {'A': 4, 'B': 6}

Solution

1. Step 1: Understand percentage representation in decimals

   Percentages are often represented as decimals between 0 and 1 in code for calculations.

2. Step 2: Evaluate options

   {'A': 0.4, 'B': 0.6} uses decimals summing to 1, correct for percentage split. {'A': 40, 'B': 60} uses integers but not decimals. {'A': '40%', 'B': '60%'} uses strings which are not directly usable. {'A': 4, 'B': 6} uses incorrect smaller numbers.

3. Final Answer:

   {'A': 0.4, 'B': 0.6} -> Option C

4. Quick Check:

   Decimal form for percentages = {'A': 0.4, 'B': 0.6} [OK]

Hint: Use decimals (0.4) not integers (40) for percentage splits [OK]

Common Mistakes:

• Using integers instead of decimals for percentages
• Using strings with % symbol in code
• Not ensuring sum equals 1

3. Given a total amount of 100 and a split strategy: {'A': 30, 'B': 70} as exact amounts, what is the amount assigned to user B?

medium

A. 70

B. 100

C. 30

D. 0

Solution

1. Step 1: Identify the split type and amounts

   The split is exact, so amounts are assigned directly as given.

2. Step 2: Find user B's assigned amount

   User B is assigned 70 as per the exact split dictionary.

3. Final Answer:

   70 -> Option A

4. Quick Check:

   Exact split assigns given amounts = 70 [OK]

Hint: Exact split means use given amounts directly [OK]

Common Mistakes:

• Adding amounts instead of reading assigned value
• Confusing exact with percentage split
• Assuming equal split when exact is given

4. In a percentage split system, if the sum of percentages provided is 110%, what is the main issue and how should it be fixed?

medium

A. The sum is valid, no fix needed

B. The sum should be exactly 0%, reset all percentages

C. The sum is less than 100%, add missing percentage

D. The sum exceeds 100%, fix by normalizing percentages to sum to 100%

Solution

1. Step 1: Identify the problem with sum of percentages

   Percentages must sum to 100% (or 1 in decimal) to correctly split amounts.

2. Step 2: Determine the fix

   If sum is 110%, it exceeds total amount. Normalize by scaling percentages so they sum to 100%.

3. Final Answer:

   The sum exceeds 100%, fix by normalizing percentages to sum to 100% -> Option D

4. Quick Check:

   Sum > 100% requires normalization [OK]

Hint: Percentages must sum to 100%, else normalize [OK]

Common Mistakes:

• Ignoring sum validation
• Assuming sum can be more than 100%
• Trying to add missing percentage when sum is too high

5. You need to design a system that supports splitting a bill among users using equal, exact, or percentage strategies. Which approach best ensures scalability and correctness when handling thousands of users?

hard

A. Allow users to input any split without checks and calculate on demand

B. Use a unified split interface that validates input and applies the correct split logic per strategy

C. Store all splits as exact amounts without validation

D. Hardcode equal split only to simplify calculations

Solution

1. Step 1: Identify requirements for scalability and correctness

   System must handle many users and ensure splits are valid and consistent.

2. Step 2: Evaluate design approaches

   Unified interface with validation ensures correctness and flexibility. Hardcoding or no validation risks errors and poor scalability.

3. Final Answer:

   Use a unified split interface that validates input and applies the correct split logic per strategy -> Option B

4. Quick Check:

   Unified validated interface = scalable & correct [OK]

Hint: Validate splits and use unified logic for scalability [OK]

Common Mistakes:

• Ignoring validation leading to incorrect splits
• Hardcoding one strategy limits flexibility
• Allowing unchecked input causes errors at scale