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LLDsystem_design~5 mins

Split strategies (equal, exact, percentage) in LLD - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What is the 'equal split' strategy in payment splitting?
Equal split means dividing the total amount evenly among all participants, regardless of individual shares or preferences.
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beginner
Explain the 'exact split' strategy.
Exact split means each participant pays a specific, predefined amount. The sum of all exact amounts equals the total bill.
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beginner
How does the 'percentage split' strategy work?
Percentage split divides the total amount based on each participant's percentage share. The sum of all percentages must be 100%.
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intermediate
What is a key challenge when implementing 'exact split' in a system?
Ensuring the sum of all exact amounts matches the total bill exactly, handling rounding errors and validation.
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intermediate
Why might 'percentage split' be preferred over 'equal split'?
Percentage split allows flexibility for participants to pay according to their consumption or agreement, unlike equal split which assumes everyone pays the same.
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Which split strategy divides the total amount evenly among all participants?
AExact split
BPercentage split
CEqual split
DRandom split
In which split strategy must the sum of all participant amounts exactly match the total bill?
AExact split
BEqual split
CPercentage split
DProportional split
What must the total of all percentages be in a percentage split?
ALess than 100%
BMore than 100%
CAny value
DExactly 100%
Which split strategy offers the most flexibility for different payment shares?
AEqual split
BPercentage split
CFixed split
DExact split
What is a common issue when implementing exact split in software?
ARounding errors causing mismatch with total
BParticipants paying too little
CParticipants paying too much
DIgnoring participant preferences
Describe the differences between equal, exact, and percentage split strategies.
Think about how the total amount is divided among participants.
You got /4 concepts.
    What are key considerations when designing a system to support multiple split strategies?
    Consider what can go wrong and how to keep the system reliable.
    You got /4 concepts.

      Practice

      (1/5)
      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