Fractal Analytics Full Stack Engineer Interview Questions and Answers

Q1. Java basic questions.
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Q2. Rest basics methods like get, post, put, delete etc
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Q3. Given a directory name, write a program to return a list of all .tst files present in the directory and its sub directories.
Ans. 
Program to return list of .tst files in given directory and subdirectories
• Use recursion to traverse through all directories and subdirectories

• Check if each file has .tst extension and add to list if true

• Use built-in functions like os.listdir() and os.path.splitext() in Python
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Q1. Difference between == and equals
Ans. 
The '==' operator is used for comparing values of primitive data types, while the 'equals' method is used for comparing objects in Java.
• Use '==' to compare primitive data types like int, char, boolean, etc.

• Use 'equals' method to compare objects like Strings, Lists, etc.

• Example: int a = 5; int b = 5; if(a == b) { // true }

• Example: String str1 = 'hello'; String str2 = 'hello'; if(str1.equals(str2)) { // true }
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Q2. Use case of abstract class and interfaces
Ans. 
Abstract classes are used to provide a common base for multiple classes, while interfaces define a contract for classes to implement.
• Abstract classes can contain both abstract and concrete methods, while interfaces can only have abstract methods.

• Abstract classes can have constructors, while interfaces cannot.

• Interfaces allow for multiple inheritance, while classes can only inherit from one abstract class.

• Abstract class...read more
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Q3. Singleton design pattern. Explain and implement (thread safe)
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Ensure a private static instance variable in the class.

• Provide a public static method to access the instance, creating it if necessary.

• Use synchronized keyword or double-checked locking to make it thread-safe.
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Q4. Merge sort. Explain and implement.
Ans. 
Merge sort is a divide and conquer algorithm that divides the input array into two halves, sorts each half, and then merges the sorted halves.
• Divide the array into two halves

• Recursively sort each half

• Merge the sorted halves back together
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Delete nodes from linkedList if their value matches a certain condition

Q1. Js advanced concepts
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Q2. Java concurrency
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Q3. Design patterns
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Q1. Implement few design patterns
Ans. 
Implementing design patterns in software development
• Singleton pattern ensures a class has only one instance and provides a global point of access to it

• Factory pattern creates objects without specifying the exact class of object that will be created

• Observer pattern defines a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated
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Q2. Questions of microservice architecture
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Q3. Java 8 tricky coding questions
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Asked me to write code on paper for count inversions

Round duration - 90 Minutes
Round difficulty - Medium

MCQ on programming basics and two coding questions. medium to hard

Q1. 0 1 Knapsack
A thief is robbing a store and can carry a maximal weight of W into his knapsack. There are N items and the ith item weighs wi and is of value vi. Considering the constraints of the maximum we...read more
Ans. 
Used Dynamic programming 2D array approach
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Round duration - 60 Minutes
Round difficulty - Easy

Interview was good and on time and questions on map,and sorting algorithms,OOPS

Q1. Longest Subarray Zero Sum
Given an array arr of length N consisting of positive and negative integers, return the length of the longest subarray whose sum is zero.
Input Format:
The first line of input c...read more
Ans. Brute Force
The brute force approach will be to calculate the sum for all possible subarrays. To calculate this, for each element(ith, where 0 <= i < N) in the array fix it as the first end of the subarray, initialize the subarray sum with zero, and iterate on the remaining elements(jth, where i <= j < N) of the array, keep adding the current element to the subarray sum and fix it as the second end of the ar...read more
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Q2. OOPS Question
oops example using code. Coding of all concepts of OOPs
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Round duration - 30 Minutes
Round difficulty - Easy

Round with Manager. Questions like why do you want to join and which tech stack you will work on

Q1. Basic HR question
what are your strength and weakness?
Ans. 
Tip 1 : You should have good communication skills
 
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Round duration - 50 Minutes
Round difficulty - Medium

It was the screening round he asked me 2 questions 
First one is easy and other one is medium type

Q1. Two Sum
You are given an array of integers 'ARR' of length 'N' and an integer Target. Your task is to return all pairs of elements such that they add up to Target.
Note:
We cannot use th...read more
Ans. Hashing Solution
• We can store the frequency of every element in the array in a hashmap.
• We will loop over every index i, and check the frequency of (Target - ARR[i]) is the hashmap:
  • If (Target - ARR[i]) is equal to ARR[i], we will check if frequency of ARR[i] . If it is greater than 1 then we will decrease the frequency of ARR[i] by 2 and add a pair (ARR[i] , ARR[i]) to our answer.
  • Else, if the frequency of ARR[i] and Targ...read more
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Q2. Root to Leaf Path
Ninja is having a good time in solving new questions of Binary Trees from Code Studio. He is now encountered with a question having statement as "You are given a binary tree consisti...read more
Ans. DFSSpace Complexity: O(1)Explanation: Time Complexity: O(1)Explanation:
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Round duration - 45 Minutes
Round difficulty - Easy

This is the first round in the loop interviews. Are you familiar with Javascript. Why do we use js. How do you use js to change the value of a textbox.

Q1. Validate BST
Given a binary tree with N number of nodes, check if that input tree is BST (Binary Search Tree) or not. If yes, return true, return false otherwise.
A binary search tree (BST) is a binary t...read more
Ans. Approach 1
• For each node, store the minimum and maximum value allowed for that node.
• Initially, for the root node as all the integer values are allowed, the minimum value would be -10^9 and the maximum value should be 10^9. Here we can also use built-in INT_MIN and INT_MAX constants.
• If the value of that node is not in the bounded range of minimum and maximum value, then return false.
• For the left subtree of a node with da...read more
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Q2. Construct Tree From Preorder Traversal
Given an array ‘pre[]’ of ‘n’ elements that represent Preorder traversal of a spacial binary tree where every node has either 0 or 2 children. Also Given a boolean ar...read more
Ans. Recursive Approach
• The idea is to construct the tree node by node.
• Take the first element of the ‘pre[]’ array. Now it is guaranteed that this will be the root node because of the definition of pre-order traversal.
• Now for any node, if ‘isLeaf’ is true it means that it is a leaf node. In this case, we create the node and return it.
• Otherwise, since the binary tree has no children or 2 children, we recursively call the func...read more
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Round duration - 45 minutes
Round difficulty - Easy

It was the team fit round

Q1. Basic HR Question
He asked me questions related to previous work in depth, projects I have worked on.
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Round duration - 45 Minutes
Round difficulty - Medium

4tn round in the loop, he asked me to design a game. He focused both on backend and frontend.
..

Q1. Bursting Balloons
You are given an array 'ARR' of N integers. Each integer represents the height of a balloon. So, there are N balloons lined up.
Your aim is to destroy all these balloons. Now, a...read more
Ans. Using hashmap
We can see here that balloons need to be destroyed in a minimum number of arrows so we need to reuse the arrows, also it’s clear that we need a new arrow for every balloon which is not getting destroyed by any previous arrow.
So we can solve this problem greedily by adding a new arrow for every balloon which is not getting destroyed by existing arrows.
• We will use a map data structure that will store the hei...read more
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Round duration - 45 Minutes
Round difficulty - Medium

Another problem solving round

Q1. Triplets with Given Sum
You are given an array/list ARR consisting of N integers. Your task is to find all the distinct triplets present in the array which adds up to a given number K.
An array is said t...read more
Ans. Brute Force
• The most trivial approach would be to find all triplets of the array and count all such triplets whose ‘SUM’ = 'K'.
• We can find the answer using three nested loops for three different indexes and check if the values at those indexes sum up to 'K'.
• Create a set  to keep the track of triplets we have visited. Run first loop from i = 0 to i = ‘N’ - 3, second loop from j = i + 1 to j = ‘N’ - 2 and third loop ...read more
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