FIS Intern Interview Questions and Answers

Round duration - 90 Minutes
Round difficulty - Medium

The test was organized online on Amcat and there were 3 coding problems. There were no MCQs in this round.

Q1. 
Ninja Technique Problem Statement
Implement a function that determines whether a given numeric string contains any substring whose integer value equals the product of two consecutive integers. The functio...read more
Ans. 
Implement a function to determine if a numeric string contains a substring whose value equals the product of two consecutive integers.
• Iterate through all substrings of the input string and check if their integer value equals the product of two consecutive integers.

• Use nested loops to generate all possible substrings efficiently.

• Check if the product of two consecutive integers matches the integer value of the substring.

• ...read more
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Q2. 
Find Nodes at a Specific Distance from Target in a Binary Tree
Given a binary tree, a target node within this tree, and an integer K, identify and return all nodes that are exactly K edges away from the t...read more
Ans. 
Find nodes at a specific distance from a target node in a binary tree.
• Traverse the binary tree to find the target node.

• Perform a depth-first search to identify nodes at distance K from the target node.

• Return the values of nodes found at distance K in an array.
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Round duration - 50 Minutes
Round difficulty - Medium

This round was scheduled by the college Training and Placement team virtually. The interviewer asked me questions pertaining mainly to DSA and we discussed my projects.

Q1. 
Segregate Even and Odd Nodes in a Linked List
You are given the head node of a singly linked list head. Your task is to modify the linked list so that all the even-valued nodes appear before all the odd-v...read more
Ans. 
Reorder a singly linked list so that all even-valued nodes appear before odd-valued nodes while preserving the original order.
• Create two separate linked lists for even and odd nodes

• Traverse the original list and move nodes to respective even or odd lists

• Merge the even and odd lists while maintaining the original order
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Round duration - 60 Minutes
Round difficulty - Easy

Again, the round was virtual. This was a Tech + Managerial round organized by the college T & P cell. The interviewer asked questions related to fundamental subjects such as Operating Systems, Object-oriented programming, and DBMS. There was one coding round at the end.

Q1. 
Diagonal Traversal of a Binary Tree
Given a binary tree of integers, find its diagonal traversal. Refer to the example for clarification on diagonal traversal.
Example:
Explanation:
Consider lines at a...read more
Ans. 
Diagonal traversal of a binary tree involves printing nodes at 135 degree angle in between lines.
• Traverse the tree in a diagonal manner, starting from the root node.

• Maintain a map to store nodes at each diagonal level.

• Print the nodes at each diagonal level in the order of traversal.
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Round duration - 40 Minutes
Round difficulty - Easy

The round was virtual and was organized by the T & P cell of the college. The interviewer asked some behavioural and situation-based questions. There was one puzzle at the end.

Round duration - 70 minutes
Round difficulty - Medium

It consisted of three coding questions varying from easy to medium.

Q1. 
Distributing Coins in a Binary Tree
You are provided with the root of a binary tree that consists of 'N' nodes. Each node in this tree contains coins, and the total number of coins across all nodes is equ...read more
Ans. 
Determine the minimum number of moves required to distribute coins in a binary tree so that every node has exactly one coin.
• Traverse the binary tree in a bottom-up manner to distribute coins efficiently.

• Keep track of the excess or deficit of coins at each node to calculate the minimum moves required.

• Transfer coins from nodes with excess coins to nodes with deficits to balance the distribution.

• Example: For the input ROO...read more
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Q2. 
Distinct Subsets Count
Given an array arr of N integers that may include duplicates, determine the number of subsets of this array containing only distinct elements.
The result should be returned modulo ...read more
Ans. 
Count the number of distinct-element subsets in an array modulo 10^9+7.
• Iterate through the array and keep track of distinct elements using a set.

• Calculate the number of subsets using the formula 2^distinct_count - 1.

• Return the result modulo 10^9+7 for each test case.
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Q3. 
0-1 Knapsack Problem Statement
A thief is robbing a store and can carry a maximal weight 'W' in his knapsack. There are 'N' items, where the i-th item has a weight 'wi' and value 'vi'. Consider the maximu...read more
Ans. 
The 0-1 Knapsack Problem involves maximizing the value of items a thief can steal within a weight limit.
• Use dynamic programming to solve the problem efficiently.

• Create a 2D array to store the maximum value that can be achieved at each weight limit.

• Iterate through the items and weights to fill the array with optimal values.

• Return the maximum value achievable at the given weight limit.
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Round duration - 60 minutes
Round difficulty - Medium

The interview was focused on data structures as well as computer fundamentals along with puzzles.

Q1. 
Sort an Array in Wave Form
You are given an unsorted array ARR. Your task is to sort it so that it forms a wave-like array.
Input:
The first line contains an integer 'T', the number of test cases.
For ea...read more
Ans. 
Sort an array in wave form where each element is greater than or equal to its adjacent elements.
• Iterate through the array and swap adjacent elements to form a wave pattern.

• Ensure that the first element is greater than or equal to the second element.

• There can be multiple valid wave arrays, so any valid wave array is acceptable.
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Q2. 
Reverse a Linked List Problem Statement
You are given a Singly Linked List of integers. Your task is to reverse the Linked List by changing the links between nodes.
Input:
The first line of input contai...read more
Ans. 
Reverse a given singly linked list by changing the links between nodes.
• Iterate through the linked list and reverse the links between nodes

• Use three pointers to keep track of the current, previous, and next nodes

• Update the links between nodes to reverse the list

• Return the head of the reversed linked list
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Round duration - 90 minutes
Round difficulty - Easy

The Round was mainly focused on resume+ dsa + system design +computer fundamentals

Q1. 
Running Median Problem
Given a stream of integers, calculate and print the median after each new integer is added to the stream.
Output only the integer part of the median.
Example:
Input:
N = 5  
Stre...read more
Ans. 
Calculate and print the median after each new integer is added to the stream.
• Use a min heap to store the larger half of the numbers and a max heap to store the smaller half.

• Keep the two heaps balanced by ensuring the size difference is at most 1.

• If the total number of elements is odd, the median is the top of the larger heap. If even, average the tops of both heaps.
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Q2. Can you explain the implementation of an LRU (Least Recently Used) Cache in a database management system?
Ans. 
LRU cache in a database management system stores most recently used data and removes least recently used data when full.
• LRU cache is implemented using a doubly linked list and a hash map.

• Each node in the linked list represents a key-value pair.

• When a key is accessed, it is moved to the front of the linked list.

• If the cache is full, the least recently used node at the end of the list is removed.

• Example: If cache size is...read more
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Q3. Design a stack that supports the getMin() operation in O(1) time and O(1) extra space.
Ans. 
Use two stacks - one to store actual values and one to store minimum values.
• Use two stacks - one to store actual values and one to store minimum values

• When pushing a new value, check if it is smaller than the current minimum and push it to the min stack if so

• When popping a value, check if it is the current minimum and pop from min stack if so

• getMin() operation can be done by peeking at the top of the min stack
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Round duration - 70 minutes
Round difficulty - Medium

Q1. 
Subtree of Another Tree Problem Statement
Given two binary trees, T and S, determine whether S is a subtree of T. The tree S should have the same structure and node values as a subtree of T.
Explanation:
...read more
Ans. 
Given two binary trees T and S, determine if S is a subtree of T with the same structure and node values.
• Traverse through tree T and check if any subtree matches tree S

• Use recursion to compare nodes of both trees

• Handle edge cases like null nodes and empty trees
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Q2. 
Generate Binary Strings with No Consecutive 1s
Given an integer K, your task is to produce all binary strings of length 'K' that do not contain consecutive '1's.
Input:
The input begins with an integer ...read more
Ans. 
Generate all binary strings of length 'K' with no consecutive '1's in lexicographically increasing order.
• Use backtracking to generate all possible binary strings without consecutive '1's.

• Start with an empty string and recursively add '0' or '1' based on the condition.

• Keep track of the current string and its length to ensure no consecutive '1's are added.

• Sort the generated strings in lexicographically increasing order b...read more
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Round duration - 60 minutes
Round difficulty - Medium

This was a data structures round.

Q1. 
Longest Consecutive Sequence Problem Statement
You are provided with an unsorted array/list ARR of N integers. Your task is to determine the length of the longest consecutive sequence present in the array...read more
Ans. 
The task is to find the length of the longest consecutive sequence in an unsorted array of integers.
• Iterate through the array and store all elements in a set for constant time lookup.

• For each element, check if it is the start of a sequence by looking for element-1 in the set.

• If it is the start, keep incrementing the count until the next element is not found in the set.
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Q2. 
Permutations Problem Statement
Given an array of distinct integers, find all possible permutations of the array.
Explanation:
A permutation is a mathematical way of determining the number of possible ar...read more
Ans. 
Find all possible permutations of an array of distinct integers.
• Use backtracking to generate all possible permutations

• Swap elements to create different permutations

• Return the permutations as an array of arrays of integers
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Round duration - 60 minutes
Round difficulty - Easy

This was a data structures round.

Q1. 
Subsequence Determination Problem
Your task is to verify if the given string STR1 is a subsequence of the string STR2. A subsequence means characters from STR2 are retained in their original order but som...read more
Ans. 
Verify if a string is a subsequence of another string by checking if characters are retained in order.
• Iterate through both strings simultaneously, checking if characters match in order.

• If a character in STR1 matches a character in STR2, move to the next character in STR2.

• If all characters in STR1 are found in STR2 in order, return True; otherwise, return False.
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Q2. 
Minimum Falling Path Sum Problem Statement
Given a square array VEC of integers with N rows and N columns, you need to determine the minimum sum of a falling path through this square array. The array has ...read more
Ans. 
Find the minimum sum of a falling path through a square array by selecting one element from each row with constraints on column selection.
• Iterate through the array from the second row, updating each element with the minimum sum of the element and its adjacent elements from the previous row.

• The minimum sum path will end in the last row with the minimum value.

• Use dynamic programming to efficiently calculate the minimum f...read more
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Round duration - 25 minutes
Round difficulty - Easy

This round was all about OS/DBMS questions.

Round duration - 45 minutes
Round difficulty - Easy

This was a technical interview round.

Q1. How does AJAX work?
Ans. 
AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes.
• AJAX stands for Asynchronous JavaScript and XML.

• It allows web pages to update content without reloading the entire page.

• AJAX uses XMLHttpRequest object to send and receive data from a server.

• Commonly used in web applications to provide a more responsive user experience.
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Q2. What is the difference between SOAP and REST?
Ans. 
SOAP is a protocol, while REST is an architectural style for web services.
• SOAP is a protocol that uses XML for message format and relies on a request-response model.

• REST is an architectural style that uses standard HTTP methods like GET, POST, PUT, DELETE.

• SOAP is more rigid and requires more bandwidth, while REST is lightweight and flexible.

• SOAP has built-in security features like WS-Security, while REST relies on exte...read more
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Q3. What is the difference between GET and POST methods in APIs?
Ans. 
GET is used to request data from a server, while POST is used to submit data to a server.
• GET requests data from a specified resource, while POST submits data to be processed to a specified resource.

• GET requests are cached by browsers, while POST requests are not.

• GET requests can be bookmarked and shared, while POST requests cannot.

• GET requests have length restrictions, while POST requests do not.

• Example: Using GET to r...read more
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Q4. What is the Observer Pattern?
Ans. 
The Observer Pattern is a behavioral design pattern where an object (subject) maintains a list of dependents (observers) that are notified of any state changes.
• Allows for one-to-many dependency between objects

• When the subject's state changes, all observers are automatically notified and updated

• Commonly used in event handling systems and GUI frameworks
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Round duration - 40 minutes
Round difficulty - Easy

This was the second technical interview round.

Q1. What is a singleton class?
Ans. 
A singleton class is a class that can only have one instance created throughout the entire application.
• Singleton classes have a private constructor to prevent multiple instances from being created.

• They typically provide a static method to access the single instance.

• Commonly used for logging, database connections, and configuration settings.
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Q2. What is meant by immutability in Java?
Ans. 
Immutability in Java refers to the property of objects whose state cannot be changed once they are created.
• Immutability ensures that once an object is created, its state cannot be modified.

• Immutable objects are thread-safe and can be shared without the risk of data corruption.

• String class in Java is an example of an immutable class.

• To create an immutable class, make the class final, all fields private, and provide only...read more
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Q3. What is dependency injection?
Ans. 
Dependency injection is a design pattern where components are given their dependencies rather than creating them internally.
• Allows for easier testing by providing mock dependencies

• Promotes loose coupling between components

• Improves code reusability and maintainability

• Examples: Constructor injection, Setter injection, Interface injection
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Q4. How do you create an immutable class in Java?
Ans. 
To create an immutable class in Java, make the class final, make all fields private and final, provide only getter methods, and do not provide any setter methods.
• Make the class final to prevent inheritance.

• Make all fields private and final to prevent modification.

• Provide only getter methods to access the fields.

• Do not provide any setter methods to modify the fields.
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Round duration - 30 minutes
Round difficulty - Easy

HR round with typical behavioral problems.