Stack Wealth Back End Engineer Interview Questions and Answers

2 questions. 1 was basic level. 2 was of medium level.

Q1. An ambiguous problem statement was given. Asking relevant questions revealed the problem to be largest island in a binary matrix. Was asked to code on an ide. And reduce space complexity to O(1).
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Q2. Maximum sum path from root to leaf in an N-ary tree. Was asked to design an appropriate data structure. Then code the solution in O(n) time and O(1) space.
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Q1. Through discuss of projects. Methods used.
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Q2. First missing positive number in an array of integer in O(n) time O(1) space.
Ans. 
Find first missing positive number in an array in O(n) time and O(1) space.
• Traverse the array and mark the presence of each positive integer by changing the sign of the corresponding index.

• Traverse the array again and return the index of the first positive integer.

• If all integers are present, return the length of the array + 1.

• Example: [3, 4, -1, 1] => mark 3rd and 4th index as negative => return 2.

• Example: [1, 2, 0] =...read more
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Q3. Given an integer, print the relevant column name in an excel sheet. Ex: 1- A , 2-B.......... 26-Z , 27-AA, 28-AB........ Was asked code on an ide and test cases were given.
Ans. 
Given an integer, print the relevant column name in an excel sheet.
• Create a string array of alphabets from A to Z

• Use modulo operator to get remainder and divide by 26 to get quotient

• Append the corresponding alphabet to the result string

• Reverse the result string
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Q1. What are your salary expectations?
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Maths,quant for 1 hour duration

Arrays, strings, linked list, palindrome

Q1. Js based question on event loop
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Q1. Question on Fundamentals of React and Javascript
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Q2. Coding question on React Native
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Q1. What are the fundamental concepts of JavaScript that were discussed during the interview?
Ans. 
Fundamental concepts of JavaScript discussed in the interview
• Data types in JavaScript (string, number, boolean, object, array)

• Functions and scope in JavaScript

• DOM manipulation and event handling

• Asynchronous programming with callbacks, promises, and async/await

• Object-oriented programming concepts in JavaScript
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Two DSA Questions
1. Check whether two strings are anagram or not?
2. Create power function without using Math.pow() library?

Design dream11. Bonus - how notification will be sent to customer for milestone of a player they have followed at scale.