Stripe is the world's leading online payment platform with incredible technology! In addition to testing algorithms, interviews also focus on code practicality and system design. Stripe's OA usually has programming and algorithm questions that are tight in time and moderately difficult, and test your ability to solve practical problems. Want to get an offer? To prepare for the exam, you need to know the techniques and answer the questions with focus. This article helps you sort out the whole process of Stripe OA + high-frequency real questions, and teaches you how to prepare for the exam efficiently. It is not a dream to get offers from big companies!
There are 2 Stripe questions, And you can find other Stripe interview questions on 1point3acres
Stripe OA 2025 Problem 1. Card Range Obfuscation
Payment card numbers consist of 8 to 19 digits, with the first six digits referred to as the Bank Identification Number (BIN). Stripe's card metadata API provides information about different card brands within each BIN range by returning mappings of card intervals to brands. to brands.
However, a given BIN range might have gaps (at the beginning, middle, or end), where no valid card numbers are present. Fraudsters may exploit these gaps to However, a given BIN range might have gaps (at the beginning, middle, or end), where no valid card numbers are present. Fraudsters may exploit these gaps to test for valid card numbers, leading to a high probability of fraud. To prevent this, the missing intervals need to be filled, ensuring the entire range is covered.
Terminology.
- BIN Range: Refers to all 16-digit card numbers starting with a specific BIN. For example, a BIN of
424242represents the range from4242420000000000To4242429999999999(inclusive). - Interval: A subset of the BIN range, inclusive of its start and end values.
Goal.
- Given a 6-digit BIN and a list of intervals corresponding to brands within the BIN range, output a sorted list of intervals that cover the entire BIN range, filling in any gaps. output a sorted list of intervals that cover the entire BIN range, filling in any gaps.
- For example, for a BIN of
424242, the task is to cover the range4242420000000000To4242429999999999.
Problem-solving ideas
This is essentially an "interval completion" problem, where you need to complete the missing intervals in a given range (BIN range) so that the final list of intervals completely covers the entire BIN range.
The complete scope needs to be determined first: Start and end values of BIN range fixed
Calculations:BIN starting value: BIN * 10^12 (e.g. 424242 * 10^12)
BIN end value: BIN * 10^12 + 10^12 - 1 (e.g. 424242 * 10^12 + 10^12 - 1)
After that, sort the input intervals: Sort the intervals in ascending order of their starting values.
Consolidated Interval:Iterate through the sorted list of intervals and merge intersecting or neighboring intervals to form a "list of valid intervals".
Fill in the missing intervals:Iterate through the merged intervals and check if there is a gap between every two neighboring intervals. If there is a gap, a new interval is created for completion.
Time Complexity:O(NlogN)
Stripe OA 2025 Problem 2: Fraudulent Merchant Detection
A model has been deployed in production, but now complaints are being received from large users such as Ticketmaster and Amazon. These users perform a large number of transactions, and some are being incorrectly flagged as fraudulent, despite most of their transactions being legitimate. These users perform a large number of transactions, and some are being incorrectly flagged as fraudulent, despite most of their transactions being legitimate. The current fraud detection threshold is too strict.
Task.
Develop a new algorithm using the percentage of fraudulent transactions (a value between 0 And 1Once marked as fraudulent, they will remain fraudulent even if their percentage drops with more transactions. Once marked as fraudulent, they will remain fraudulent even if their percentage drops with more transactions.
Additionally, the algorithm will require a minimum number of transactions for a merchant to be evaluated.
Problem-solving ideas
- Record the status of merchants:
- A status variable is maintained for each merchant that is used to mark whether the merchant is considered a fraudulent merchant.
- Once the status is set to Fraudulent Merchant, it will not be revoked.
- Calculation of fraud rate:
- Fraud rate formula for merchants: Fraud rate = Number of fraudulent transactions / Total number of transactions
- Each time a new transaction occurs, the number of fraudulent transactions and the total number of transactions are updated and the fraud rate is recalculated.
- Inspection and evaluation of conditions:
- After each update, check if the merchant has reached the minimum number of transactions.
- If the minimum number of transactions is reached and the current fraud rate exceeds the threshold, the merchant is flagged as fraudulent.
- implementation logic:
- Record transaction data for all merchants, including the total number of transactions, the number of fraudulent transactions, and the current status (whether or not they are flagged as fraudulent).
- Each time a new transaction is processed, the merchant's transaction data is updated and the status is re-evaluated based on the legitimacy of the transaction.
Reference
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