BlackBuck Software Developer Interview Questions and Answers

Q1. Tell me about you
Ans. 
I am a passionate software developer with a strong background in programming languages such as Java, Python, and JavaScript.
• Experienced in developing web applications using frameworks like Spring Boot and React

• Proficient in database management with SQL and NoSQL databases

• Skilled in problem-solving and debugging code efficiently
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Q1. Voting Algo n/2 element
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Q1. DSA ROUND - DP problem
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Dynamic Programming problem involving finding the maximum sum of non-adjacent elements in an array.
• Use dynamic programming to keep track of the maximum sum at each index.

• At each index, the maximum sum is either the current element plus the sum two indices back, or the sum at the previous index.

• Example: For array [2, 4, 6, 2, 5], the maximum sum of non-adjacent elements is 13 (2 + 6 + 5).
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Q2. DSA ROUND - STRING PROBLEM
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Find the longest common prefix among an array of strings.
• Iterate through the characters of the first string and compare with other strings

• Return the prefix when characters don't match or reach end of any string

• Example: Input - ['flower', 'flow', 'flight'], Output - 'fl'
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Q1. PROJECT RELATED QUESTIONS
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Q2. DESIGN LRU CACHE
Ans. 
LRU cache is a data structure that stores the most recently used items.
• Use a doubly linked list to keep track of the order of items based on their usage.

• Use a hashmap to quickly access items in the cache.

• When a new item is accessed, move it to the front of the linked list.

• If the cache is full, remove the least recently used item from the end of the linked list.
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Q1. What is oops concepts
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OOPs concepts are the fundamental principles of object-oriented programming.
• Encapsulation - binding data and functions together in a single unit

• Inheritance - creating new classes from existing ones

• Polymorphism - ability of objects to take on many forms

• Abstraction - hiding implementation details from the user

• Examples: class, object, inheritance, encapsulation, polymorphism, abstraction
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Q2. What is spring boot
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Spring Boot is a framework for building standalone, production-grade Spring-based applications.
• Spring Boot simplifies the process of creating and deploying Spring-based applications.

• It provides a set of pre-configured dependencies and an embedded web server.

• It also offers features like auto-configuration, which reduces the need for manual configuration.

• Spring Boot is widely used for building microservices and RESTful A...read more
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Round duration - 90 minutes
Round difficulty - Medium

This was a Data Structures round. Both questions were answered in optimal time complexity with clean code. Every other question was answered to the best of my knowledge

Q1. 
Rotting Oranges Problem Statement
You are given an undirected and disconnected graph G(V, E) with V vertices numbered from 0 to V-1 and E edges. Your task is to perform a BFS traversal starting from the 0...read more
Ans. 
Perform BFS traversal on an undirected and disconnected graph starting from vertex 0.
• Implement BFS traversal algorithm starting from vertex 0

• Use a queue to keep track of visited nodes and their neighbors

• Print the traversal order in sorted order for each node's connected nodes
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Q2. 
Smallest Integer Not Representable as Subset Sum
Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from...read more
Ans. 
Find the smallest positive integer that cannot be expressed as the sum of elements from any proper subset of a non-decreasing sorted array of positive numbers.
• Start with the smallest possible sum that can be represented, which is 1.

• Iterate through the array and update the smallest sum that cannot be represented.

• Return the final smallest sum that cannot be represented.
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Q3. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal of an undirected and disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Use a queue to keep track of visited nodes and their neighbors.

• Ensure to visit all connected components of the graph.

• Print the BFS traversal sequence for each test case in a separate line.

• Handle cases where not all vertices are reachable from vertex 0.
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Round duration - 100 minutes
Round difficulty - Easy

Mostly technical and System Design questions were asked.

Q1. Design an LRU (Least Recently Used) cache.
Ans. 
Design an LRU cache to store least recently used items efficiently.
• Use a combination of a doubly linked list and a hashmap to store and retrieve items in O(1) time complexity.

• When an item is accessed, move it to the front of the linked list to mark it as the most recently used.

• If the cache is full, remove the least recently used item from the end of the linked list and the hashmap.
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