Fidelity International Software Developer Interview Questions and Answers

Round duration - 90 minutes
Round difficulty - Medium

There were 33 questions in total. The objective questions were simple.

Q1. 
Sort Big List Dates Problem Statement
Mary is an enthusiastic party-goer who struggles with remembering event dates. Help Mary by sorting a given list of event dates in an ascending order.
Example:
Inpu...read more
Ans. 
Sort a list of event dates in ascending order based on year, month, and day.
• Sort the list of dates based on year, then month, and finally day.

• Use a sorting algorithm to rearrange the dates in ascending order.

• Ensure the constraints are met for each date in the list.
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Q2. 
Pair Sum Problem Statement
You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to find and return a list of all pairs of elements where each sum of a pair equals 'S'.
Note:
...read more
Ans. 
Given an array and a target sum, find all pairs of elements that add up to the target sum.
• Iterate through the array and for each element, check if the complement (target sum - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the pairs based on the first element and then the second element.

• Handle edge cases like duplicate elements and pairs with the same values.

• Example...read more
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Q3. 
Maximum Sum Problem Statement
Given an integer N, your task is to recursively break it into three integer parts: N / 2, N / 3, and N / 4. You need to compute the maximum sum possible by dividing the numbe...read more
Ans. 
Given an integer N, recursively break it into three parts and find the maximum sum possible.
• Recursively divide N into N/2, N/3, and N/4 to find the maximum sum

• Compare the sum obtained by dividing N with the sum of N itself

• Return the maximum sum for each test case
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Round duration - 60 minutes
Round difficulty - Medium

Technical Interview round with questions based on DSA.

Q1. 
Duplicate Integer in Array
Given an array ARR of size N, containing each number between 1 and N-1 at least once, identify the single integer that appears twice.
Input:
The first line contains an integer...read more
Ans. 
Identify the duplicate integer in an array containing numbers between 1 and N-1.
• Iterate through the array and keep track of the frequency of each element using a hashmap.

• Return the element with a frequency greater than 1 as the duplicate integer.

• Ensure the constraints are met and a duplicate number is guaranteed to be present.
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Q2. 
Sum Root to Leaf Numbers
You are given an arbitrary binary tree consisting of N nodes, each associated with an integer value from 1 to 9. Each root-to-leaf path can be considered a number formed by concat...read more
Ans. 
Calculate the total sum of all root to leaf paths in a binary tree formed by concatenating node values.
• Traverse the binary tree from root to leaf nodes, keeping track of the current path sum

• Add the current node value to the path sum and multiply by 10 for each level

• When reaching a leaf node, add the final path sum to the total sum

• Return the total sum modulo (10^9 + 7)
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Q3. 
Topological Sort Problem Statement
You are given a directed acyclic graph (DAG). Your task is to perform topological sorting of the graph and return any valid ordering.
Explanation:
A directed acyclic g...read more
Ans. 
Implement a function to perform topological sorting on a directed acyclic graph (DAG) and return any valid ordering.
• Create a graph data structure to represent the DAG

• Use depth-first search (DFS) to perform topological sorting

• Maintain a visited array to keep track of visited nodes

• Return the ordering of nodes after DFS traversal
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Round duration - 60 minutes
Round difficulty - Easy

Technical interview round with questions based on DSA.

Q1. 
LCA of Binary Tree Problem Statement
You are given a binary tree consisting of distinct integers and two nodes, X and Y. Your task is to find and return the Lowest Common Ancestor (LCA) of these two nodes...read more
Ans. 
Find the Lowest Common Ancestor (LCA) of two nodes in a binary tree.
• Traverse the binary tree to find the paths from the root to nodes X and Y.

• Compare the paths to find the last common node, which is the LCA.

• Handle cases where one node is an ancestor of the other.

• Consider edge cases like when X or Y is the root node.

• Implement a recursive or iterative solution to find the LCA efficiently.
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Q2. 
Rotated Array Minimum Finder
You are provided with a sorted array that has undergone 'K' rotations (the exact value of 'K' is unknown). A rotation involves shifting each element of the array to the right,...read more
Ans. 
Implement a function to find the minimum number in a rotated sorted array efficiently.
• Use binary search to find the minimum element in the rotated array.

• Compare the mid element with the start and end elements to determine which half of the array to search next.

• Continue the binary search until the minimum element is found.
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Q3. 
Maximum Binary Tree Construction Problem
Given an array TREE of 'N' unique integers, construct a maximum binary tree using the following rules:
1. The root of this tree is the maximum number in TREE.
2. T...read more
Ans. 
Construct a maximum binary tree from an array of unique integers following specific rules.
• Find the maximum number in the array to set as the root of the tree.

• Recursively construct the left subtree with elements before the maximum number.

• Recursively construct the right subtree with elements after the maximum number.
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Round duration - 60 minutes
Round difficulty - Easy

The interviewer called my via phone and simultaneously provided me a link where I had to write the code for a given problem. It was scheduled at 12:30 pm, so timing was not an issue. It was a standard DP question involving a 2D matrix. The question was easy and I was able to code it within given time.

Round duration - 60 minutes
Round difficulty - Easy

The interviewer asked me two coding questions in this round.

Q1. Write an efficient program to find the sum of the contiguous subarray within a one-dimensional array of numbers that has the largest sum.
Ans. 
Efficient program to find sum of largest contiguous subarray within a one-dimensional array.
• Use Kadane's algorithm to find the maximum sum subarray in O(n) time complexity.

• Initialize max_sum and current_sum to 0, iterate through array updating current_sum and max_sum.

• Return max_sum as the result.
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Round duration - 60 minutes
Round difficulty - Easy

This was on-site round at their Bangalore office. The interviewer was friendly and helpful. The interview held inside a conference room.

Q1. 
DFS Traversal Problem Statement
Given an undirected and disconnected graph G(V, E), where V is the number of vertices and E is the number of edges, the connections between vertices are provided in the 'GR...read more
Ans. 
DFS traversal problem to find connected components in an undirected and disconnected graph.
• Use Depth First Search (DFS) algorithm to traverse the graph and find connected components

• Maintain a visited array to keep track of visited vertices

• Iterate through all vertices and perform DFS on unvisited vertices to find connected components
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Round duration - 60 minutes
Round difficulty - Easy

This was the next round of the onsite interviews. Took place in the same conference room as that of the previous round.

Round duration - 60 minutes
Round difficulty - Easy

This was the third round of the onsite interview. 
 

Round duration - 87 minutes
Round difficulty - Medium

Timing : It was conducted in evening at 3 PM
The pacreception environment was very user friendly .
The platform was audio and video proctored.

Q1. 
Binary to Decimal Conversion
Convert a given binary number, represented as a string 'S' of size 'N', into its decimal equivalent integer and output it.
Input:
The first line contains an integer 'T', den...read more
Ans. 
Convert a binary string to its decimal equivalent integer.
• Iterate through the binary string from right to left, multiplying each digit by 2 raised to the power of its position.

• Add the results of the multiplication to get the decimal equivalent.

• Ensure the binary string consists only of '0' and '1' characters.

• Handle multiple test cases by repeating the conversion process for each case.
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Round duration - 80 minutes
Round difficulty - Medium

So This was a very interactive round . There were two interviewers , one male and one female . The male interviewer was quite experienced where as female interviewer was relatively new . The Interview started by a small introduction followed by some OOPS related questions where I was tested on how i perceive the concept of OOPS in real life . Then this conversation was followed by some core concepts of JAVA like abstract classes and interfaces . Then I was asked about my projects that i mentioned in my resume , then after some healthy discussion on those projects , the interviewer started to question about DBMS , I was asked some basic queries followed by some advanced queries and then followed by a discussion on SQL vs NoSQL . Then Interviewers asked me about my tech stack and the source of my technical knowledge. Then at last I was asked that why Blackrock and this concluded my Interview.

Q1. 
Ninja And The Triangle Problem Statement
Ninja is provided with 'N' stars and the task is to construct a triangle such that the 'i'th level of the triangle uses 'i' number of stars. The goal is to make th...read more
Ans. 
Given 'N' stars, construct a triangle with maximum height using 'i' stars in 'i'th level.
• Calculate the maximum height of the triangle using the formula: height = floor((-1 + sqrt(1 + 8 * N)) / 2)

• Iterate through each test case and calculate the maximum height for each 'N'.

• Output the maximum height for each test case.
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Q1. Java questions , stream api
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Q2. Whatever you have mention in resume
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Round duration - 100 Minutes
Round difficulty - Hard

There were 2 interviewers. It started with an introduction from me and one of the interviewers directly started with a DSA questions. Two problems were asked and I had to code them on a compiler of my choice by sharing my screen. Level of DSA question was medium but I was severely grilled on oops. I had to create different abstract classes, interface and explain entire oops with examples.

This was followed by a set of core JAVA questions :

Difference between == and .equals() ?
Mention some methods of the object class?
Difference between TreeSet and SortedSet?
How is a String saved in JAVA?
difference between string pool and heap memory?

Q1. 
Shortest Distance in a Binary Search Tree
Your task is to determine the shortest distance between two nodes with given keys in a Binary Search Tree (BST).
It is assured that both keys exist within the BS...read more
Ans. 
Find the shortest distance between two nodes in a Binary Search Tree.
• Traverse the BST to find the paths from the root to both nodes.

• Compare the paths to find the common ancestor node.

• Calculate the distance by adding the lengths of the paths from the common ancestor to both nodes.

• Return the shortest distance as the result.
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Q2. 
Greatest Common Divisor Problem Statement
You are tasked with finding the greatest common divisor (GCD) of two given numbers 'X' and 'Y'. The GCD is defined as the largest integer that divides both of the...read more
Ans. 
Find the greatest common divisor (GCD) of two given numbers 'X' and 'Y'.
• Iterate from 1 to the minimum of X and Y, check if both X and Y are divisible by the current number, update GCD if true

• Use Euclidean algorithm to find GCD: GCD(X, Y) = GCD(Y, X % Y)

• If one of the numbers is 0, the other number is the GCD

• Handle edge cases like when one of the numbers is 0 or negative
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Q3. 
Bridge in Graph Problem Statement
Given an undirected graph with V vertices and E edges, your task is to find all the bridges in this graph. A bridge is an edge that, when removed, increases the number of...read more
Ans. 
Find all the bridges in an undirected graph.
• Use Tarjan's algorithm to find bridges in the graph.

• A bridge is an edge whose removal increases the number of connected components.

• Check for bridges by removing each edge and running a DFS to see if the graph is still connected.
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Round duration - 90 Minutes
Round difficulty - Medium

Round duration - 60 Minutes
Round difficulty - Medium

Q1. 
Validate Binary Search Tree Problem Statement
Your task is to determine if a given binary tree with 'N' nodes is a valid Binary Search Tree (BST). A BST is defined by the following properties:
• The lef...read more
Ans. 
Validate if a given binary tree is a valid Binary Search Tree (BST) based on its properties.
• Check if the left subtree of a node has only nodes with data less than the node's data.

• Verify if the right subtree of a node has only nodes with data greater than the node's data.

• Ensure that both the left and right subtrees are also binary search trees.

• Implement a validation function for a BST.

• Output 'true' if the binary tree is
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Round duration - 60 Minutes
Round difficulty - Easy