Pixis Software Developer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Easy

Q1. 
Level Order Traversal Problem Statement
Given a binary tree of integers, return the level order traversal of the binary tree.
Input:
The first line contains an integer 'T', representing the number of te...read more
Ans. 
Return the level order traversal of a binary tree given in level order with null nodes represented by -1.
• Create a queue to store nodes for level order traversal

• Start with the root node and add it to the queue

• While the queue is not empty, dequeue a node, print its value, and enqueue its children

• Repeat until all nodes are traversed in level order
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Round duration - 45 minutes
Round difficulty - Easy

Q1. What is a deadlock in DBMS, and can you explain the concepts of join and query?
Ans. 
A deadlock in DBMS occurs when two or more transactions are waiting for each other to release locks, causing them to be stuck indefinitely.
• Deadlock is a situation where two or more transactions are unable to proceed because each is waiting for the other to release locks.

• To prevent deadlocks, DBMS uses techniques like deadlock detection and prevention algorithms.

• Joins in DBMS are used to combine rows from two or more ta...read more
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. Design a system for Twitter, outlining the key components and architecture involved.
Ans. 
Design a system for Twitter
• Key components: user profiles, tweets, hashtags, timelines

• Architecture: microservices, load balancers, databases, caching

• Scalability: sharding, replication, CDN

• Real-time processing: streaming APIs, push notifications
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Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Maximum Subarray Sum Queries
You are provided with an array of ‘N’ integers and ‘Q’ queries. Each query requires calculating the maximum subarray sum in a specified range of the array.
Input:
The first ...read more
Ans. 
Implement a function to calculate maximum subarray sum queries in a given range of an array.
• Iterate through each query and calculate the maximum subarray sum within the specified range using Kadane's algorithm.

• Keep track of the maximum sum found so far and update it as needed.

• Return the maximum subarray sum for each query in the test case.
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use a single scan over the array to sort it in-place.

• Maintain three pointers for 0s, 1s, and 2s and swap elements accordingly.

• Example: Input: [0, 2, 1, 2, 0], Output: [0, 0, 1, 2, 2]
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Round duration - 20 Minutes
Round difficulty - Medium

1st round is coding assessment round based on graph and hashmaps

5 verbal questions, 2 mid - hard coding on arrays, hashmap and dp

Q1. Introduce yourself and projects
Ans. 
I am a software developer with experience in web development and mobile applications.
• Developed a web application using React and Node.js for managing inventory

• Created a mobile app using Flutter for tracking daily expenses

• Familiar with Agile development practices
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Q2. Basic questions on coding define different DS and Difference btw them
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Q1. Explain hoisting in js
Ans. 
Hoisting in JavaScript is the behavior where variable and function declarations are moved to the top of their containing scope during the compilation phase.
• Variable declarations are hoisted to the top of their scope, but not their assignments.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

• Hoisting can lead to unexpected behavior if not understood properly.
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Q2. Explain closures in js
Ans. 
Closures in JavaScript allow functions to access variables from their outer scope even after the outer function has finished executing.
• Closures are created when a function is defined within another function and the inner function has access to the outer function's variables.

• Closures can be used to create private variables and functions in JavaScript.

• Closures can also be used to maintain state in asynchronous operations
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Q1. Javascript polyfills
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Round duration - 90 minutes
Round difficulty - Hard

They gave around 7 days of time for attending the test.
It had 4 coding questions out of which I solved 2 fully and 2 partially. 
Questions were medium-hard and based on DSA.

Q1. 
Find the Third Greatest Element
Given an array 'ARR' of 'N' distinct integers, determine the third largest element in the array.
Input:
The first line contains a single integer 'T' representing the numb...read more
Ans. 
Find the third largest element in an array of distinct integers.
• Sort the array in descending order and return the element at index 2.

• Handle cases where the array has less than 3 elements separately.

• Consider edge cases like negative integers and duplicates.
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Q2. 
Wildcard Pattern Matching Problem Statement
Implement a wildcard pattern matching algorithm to determine if a given wildcard pattern matches a text string completely.
The wildcard pattern may include the...read more
Ans. 
Implement a wildcard pattern matching algorithm to determine if a given wildcard pattern matches a text string completely.
• Create a recursive function to match the pattern with the text character by character.

• Handle cases for '?' and '*' characters in the pattern.

• Use dynamic programming to optimize the solution.

• Check for edge cases like empty pattern or text.
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Q3. 
Detect and Remove Loop in Linked List
For a given singly linked list, identify if a loop exists and remove it, adjusting the linked list in place. Return the modified linked list.
Expected Complexity:
A...read more
Ans. 
Detect and remove loop in a singly linked list with O(n) time complexity and O(1) space complexity.
• Use Floyd's Cycle Detection Algorithm to identify the loop in the linked list.

• Once the loop is detected, use two pointers to find the start of the loop.

• Adjust the pointers to remove the loop and return the modified linked list.

• Example: For input 5 2 and elements 1 2 3 4 5, output should be 1 2 3 4 5.
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Q4. 
Longest Common Subsequence Problem Statement
Given two strings STR1 and STR2, determine the length of their longest common subsequence.
A subsequence is a sequence that can be derived from another sequen...read more
Ans. 
The task is to find the length of the longest common subsequence between two given strings.
• Implement a function to find the longest common subsequence length.

• Use dynamic programming to solve the problem efficiently.

• Iterate through the strings to find the common subsequence.

• Handle edge cases like empty strings or equal strings.

• Example: For input 'abcde' and 'ace', the longest common subsequence is 'ace' with a length of
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Round duration - 60 Minutes
Round difficulty - Easy

Formal Introduction.
Asked About Projects.
Difference between SQL and NoSQL. Pros and Cons. Where should we use SQL and NoSQL.
Given a problem, I have to make a SQL Database structure and then interviewer told me to convert it into NoSQL.
asked coding questions

Q1. 
Search In Rotated Sorted Array Problem Statement
Given a sorted array of distinct integers that has been rotated clockwise by an unknown amount, you need to search for a specified integer in the array. Fo...read more
Ans. 
Implement a search function to find a specified integer in a rotated sorted array.
• Implement a binary search algorithm to find the target integer in the rotated sorted array.

• Handle the cases where the target integer may lie in the left or right half of the rotation.

• Keep track of the mid element and adjust the search range based on the rotation.

• Return the index of the target integer if found, else return -1.
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Q2. 
Zigzag Binary Tree Traversal Problem
Given a binary tree, compute the zigzag level order traversal of the node values in the tree. The zigzag traversal requires traversing levels from left to right, then ...read more
Ans. 
Zigzag level order traversal of a binary tree is computed by alternating between left to right and right to left traversal at each level.
• Use a queue to perform level order traversal of the binary tree.

• Maintain a flag to switch between left to right and right to left traversal at each level.

• Store the node values in a list while traversing and alternate the order based on the flag.

• Example: For input 1 2 3 4 -1 5 6 -1 7 -...read more
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