Cashfree Payments Interview Questions and Answers

Twenty mcqs on logical thinking, aptitude and mathematical ability and two coding questions.
First question - given a string and a number k delete all characters that appear k times consequetively and repeat in the new result string till no further deletion is possible.
Second question - given an array with m non-zero numbers and rest 0 determine the minimum number of exchanges between a non-zero number and a 0 to put all the zero to the right of the array.

Q1. Find the number of buildings to the left and right that can be viewed from the top of each building in a sequence of buildings.
Ans. 
Given a sequence of buildings, find the number of buildings visible to the left and right from the top of each building.
• Traverse the sequence of buildings from left to right and maintain a stack of visible buildings.

• For each building, pop all the buildings from the stack that are shorter than the current building and count them as visible to the left.

• Push the current building onto the stack and count the number of buil...read more
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Q1. One recursion based coding question to be solved in JS.
Ans. 
Recursion is a method where a function calls itself to solve a problem, often simplifying complex tasks.
• Recursion involves a base case and a recursive case.

• Example: Calculating factorial of a number n: factorial(n) = n * factorial(n-1).

• Base case: factorial(0) = 1.

• Recursion can lead to elegant solutions for problems like tree traversals and Fibonacci series.
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Q2. Two questions that were a follow up to the 1st question.
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Q1. React Native framework based questions
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Q2. Release process of an app on Play Store and apple store
Ans. 
The release process involves preparing the app for submission, testing, uploading to the respective app stores, and managing the release.
• Prepare the app for submission by ensuring it meets all guidelines and requirements of the app stores.

• Test the app thoroughly to identify and fix any bugs or issues before release.

• Upload the app to the Play Store and Apple Store developer consoles.

• Manage the release by setting up rele...read more
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Q3. Creation of Custom hook
Ans. 
Custom hooks in React Native allow for reusable logic across components.
• Custom hooks are functions that start with 'use' keyword.

• They can encapsulate logic like API calls, state management, etc.

• Example: useFetch custom hook for making API calls.
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Q4. Tools discussion for RN app, specifically Firebase, Sentry.
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The interviewer asked me to build an accordion, the interview was 1 hour long

Q1. Rate Limiting algorithm
Ans. 
Rate limiting algorithm is used to control the rate of traffic sent or received by a system.
• Rate limiting helps prevent abuse, protect against DoS attacks, and ensure fair usage of resources.

• Common rate limiting algorithms include token bucket, leaky bucket, and fixed window.

• Token bucket algorithm allows bursts of traffic up to a certain limit, while leaky bucket algorithm smooths out traffic over time.

• Fixed window alg...read more
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Q2. HTTP status codes
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Q1. Convert Arabic to Roman numeral
Ans. 
Convert Arabic numbers to Roman numerals
• Create a mapping of Arabic numbers to Roman numerals

• Iterate through the mapping to find the largest Roman numeral that fits the Arabic number

• Subtract the value of the Roman numeral from the Arabic number and repeat until the Arabic number becomes 0
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