Evolent Health International Software Developer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

The interviewer asked me 2 questions related to DS/Algo in this round . Both the questions were of Easy-Medium difficulty and I was also required to code them in a production ready manner.

Q1. 
Maximum Sum Path in a Binary Tree Problem Statement
You are provided with a binary tree consisting of N nodes where each node has an integer value. The task is to determine the maximum sum achievable by a...read more
Ans. 
Find the maximum sum achievable by a simple path between any two nodes in a binary tree.
• Traverse the binary tree to find all possible paths and calculate their sums.

• Keep track of the maximum sum encountered during traversal.

• Consider paths that may include the same node twice.

• Implement a recursive function to explore all possible paths.

• Handle cases where nodes have negative values.
Answered by AI
Add your answer
Q2. 
Intersection of Two Arrays Problem Statement
Given two arrays A and B with sizes N and M respectively, both sorted in non-decreasing order, determine their intersection.
The intersection of two arrays in...read more
Ans. 
The problem involves finding the intersection of two sorted arrays efficiently.
• Use two pointers to iterate through both arrays simultaneously.

• Compare elements at the pointers and move the pointers accordingly.

• Handle cases where elements are equal, and update the intersection array.

• Return the intersection array as the result.
Answered by AI
Add your answer

Round duration - 50 Minutes
Round difficulty - Medium

This round had 2 questions of DS/Algo to solve under 50 minutes and one question related to Operating Systems.

Q1. 
Next Greater Element Problem Statement
You are provided with an array or list ARR containing N positive integers. Your task is to determine the Next Greater Element (NGE) for each element in the array.
T...read more
Ans. 
Find the Next Greater Element for each element in an array.
• Iterate through the array from right to left

• Use a stack to keep track of elements with no greater element to the right

• Pop elements from the stack until finding a greater element or stack is empty
Answered by AI
Add your answer
Q2. 
Number In Arithmetic Progression Problem
Given three integers X, C, and Y, where X is the first term of an arithmetic sequence with a common difference of C, determine if Y is part of this arithmetic sequ...read more
Ans. 
Check if a given number is part of an arithmetic sequence with a given first term and common difference.
• Calculate the arithmetic sequence using the formula: nth term = X + (n-1) * C

• Check if Y is equal to any term in the sequence to determine if it belongs to the sequence

• Return 'True' if Y belongs to the sequence, otherwise return 'False'
Answered by AI
Add your answer
Q3. Can you define process and threads in operating systems?
Ans. 
Processes are instances of programs in execution, while threads are smaller units within a process that can execute independently.
• A process is a program in execution, consisting of code, data, and resources.

• Threads are smaller units within a process that can execute independently.

• Processes have their own memory space, while threads share the same memory space within a process.

• Processes are heavyweight, while threads ar...read more
Answered by AI
Add your answer

Round duration - 50 Minutes
Round difficulty - Medium

This round had 2 questions of DSA of Easy-Medium difficulty and at the end I was asked a Puzzle to check my general problem solving ability.

Q1. 
Max Product Subset Problem Statement
Given an array/list arr of size n, determine the maximum product possible by taking any subset of the array/list arr. Return the result modulo 10^9+7 since the product ...read more
Ans. 
Find the maximum product of a subset of an array modulo 10^9+7.
• Iterate through the array and keep track of the maximum positive product and minimum negative product encountered so far.

• Handle cases where the array contains zeros separately.

• Return the maximum product modulo 10^9+7.
Answered by AI
Add your answer
Q2. 
Populating Next Right Pointers in Each Node
Given a complete binary tree with 'N' nodes, your task is to determine the 'next' node immediately to the right in level order for each node in the given tree.
...read more
Ans. 
Implement a function to update 'next' pointers in a complete binary tree.
• Iterate level by level using a queue

• Connect nodes at each level using 'next' pointers

• Handle null nodes appropriately

• Ensure the tree is a complete binary tree
Answered by AI
Add your answer
Q3. You have two wires of different lengths that are both capable of burning for exactly one hour when ignited at both ends. How can you measure a time interval of 45 minutes using these two wires?
Add your answer

Round duration - 50 Minutes
Round difficulty - Medium

This round consisted of 2 questions from DSA where I was first asked to explain my approach to the interviewer with proper complexity analysis and then code the problems. The interviewer was quite friendly and also provided me some hints when I was stuck.

Q1. 
Stack with getMin Operation
Create a stack data structure that supports not only the usual push and pop operations but also getMin(), which retrieves the minimum element, all in O(1) time complexity witho...read more
Ans. 
Implement a stack with push, pop, top, isEmpty, and getMin operations in O(1) time complexity without using extra space.
• Use two stacks - one to store the actual elements and another to store the minimum element at each level.

• When pushing an element, check if it is smaller than the current minimum and update the minimum stack accordingly.

• When popping an element, also pop from the minimum stack if the popped element is t...read more
Answered by AI
Add your answer
Q2. 
Split Array Into Maximum Subarrays Problem Statement
You are given an integer array arr of size N. Your task is to split the array into the maximum number of subarrays such that the first and last occurre...read more
Ans. 
Given an array, split it into maximum subarrays with first and last occurrence of each element in a single subarray.
• Iterate through the array and keep track of the first and last occurrence of each element.

• Use a hashmap to store the indices of each element.

• Split the array whenever the last occurrence of an element is found.
Answered by AI
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

This was a test round where 10 aptitude based questions were to be solved in 60 minutes

Q1. You have 5 pirates and 100 gold coins. The challenge is to determine how the pirates will divide the coins among themselves based on their ranking and the rules they follow.
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

They took us to the lab for this on and we were each given a paper with a program on it. It was all mixed as in each person got a different paper, You have around an hour to finish coding. after which you have to explain your code. They also gave wrong or incorrect inputs and see how your code handles these exceptions.

Q1. 
Reverse the String Problem Statement
You are given a string STR which contains alphabets, numbers, and special characters. Your task is to reverse the string.
Example:
Input:
STR = "abcde"
Output:
"e...read more
Ans. 
Reverse a given string containing alphabets, numbers, and special characters.
• Iterate through the string from the end to the beginning and append each character to a new string.

• Use built-in functions like reverse() or StringBuilder in languages like Python or Java for efficient reversal.

• Handle special characters and numbers along with alphabets while reversing the string.

• Ensure to consider the constraints provided in th...read more
Answered by AI
Add your answer
Q2. 
K Largest Elements Problem Statement
Given an unsorted array containing 'N' integers, you are required to find 'K' largest elements from the array and return them in non-decreasing order.
Input:
The fir...read more
Ans. 
Implement a function to find K largest elements in an unsorted array in non-decreasing order.
• Create a min heap of size K and insert the first K elements of the array

• For each remaining element, if it is larger than the root of the heap, replace the root with the element and heapify

• Finally, the heap will contain the K largest elements in non-decreasing order
Answered by AI
Add your answer
Q3. 
Remove Character from String Problem Statement
Given a string str and a character 'X', develop a function to eliminate all instances of 'X' from str and return the resulting string.
Input:
The first lin...read more
Ans. 
Develop a function to remove all instances of a given character from a string.
• Iterate through the string and build a new string excluding the specified character.

• Use a StringBuilder or similar data structure for efficient string manipulation.

• Handle edge cases like empty string or character not found in the input string.

• Ensure the function completes within the given time constraint.
Answered by AI
Add your answer
Q4. 
Triangle of Numbers Pattern
Ninja is tasked with printing a triangle pattern based on a given number 'N' for any test case.
Example:
Input:
N = 4
Output:
   1
  232
 34545
4567654
Explanation:
The pat...read more
Ans. 
Print a triangle pattern of numbers based on a given number 'N'.
• Iterate through each row and column to determine the numbers to print

• Use a combination of spaces and numbers to align the pattern correctly

• Increment the numbers in each row based on the row number
Answered by AI
Add your answer

Round duration - 60 minutes
Round difficulty - Easy

Compared to the other round this is more tech oriented. Lot more tech questions. It is of normal difficulty and is not that hard to clear, you only need to know the basics.
Very basic of Data Structure and Oracle knowledge enough. Lots of simple questions from data structures(insert into heaps etc). They did not ask to write code for DS, but rather to explain the logic through diagrams. For some complicated question, they expect how much you brainstorm ideas in solving

Q1. 
Convert Binary Tree to Mirror Tree
Convert a given binary tree into its mirror tree, where the left and right children of all non-leaf nodes are interchanged.
Input:
An integer ‘T’ denoting the number o...read more
Ans. 
Convert a binary tree into its mirror tree by interchanging left and right children of non-leaf nodes.
• Traverse the tree in postorder fashion and swap the left and right children of each node.

• Use recursion to solve the problem efficiently.

• Modify the binary tree in place without creating a new tree.
Answered by AI
Add your answer
Q2. 
Heap Sort Problem Statement
Given an array ARR consisting of N integers, your task is to use the Heap sort algorithm to arrange the array in non-decreasing order.
Input:
The first line of the input cont...read more
Ans. 
Implement the Heap sort algorithm to arrange an array in non-decreasing order.
• Implement the Heap sort algorithm to sort the given array in non-decreasing order

• Use a max heap to sort the array in non-decreasing order

• Time complexity of Heap sort is O(n log n)
Answered by AI
Add your answer
Q3. What is indexing in the context of databases?
Ans. 
Indexing in databases is a technique used to improve the speed of data retrieval by creating a data structure that allows for quick lookups.
• Indexes are created on specific columns in a database table to speed up queries that search for data in those columns.

• Indexes work similar to the index of a book, allowing the database to quickly locate the desired data without having to scan the entire table.

• Examples of indexes in...read more
Answered by AI
Add your answer
Q4. Which data structure is better for your use case: a B Tree or a Hash Table?
Ans. 
Hash Table is better for fast lookups and insertions, while B Tree is better for range queries and ordered traversal.
• Use Hash Table for fast lookups and insertions with O(1) average time complexity.

• Use B Tree for range queries and ordered traversal with O(log n) time complexity.

• Consider the size of the dataset and the specific operations needed to determine the best data structure.
Answered by AI
Add your answer

Round duration - 30 minutes
Round difficulty - Easy

This round lasted for around 30 minutes. It more of a character analysis round with a lot of HR type questions.

Round duration - 60 minutes
Round difficulty - Easy

10 Aptitude questions with difficulty level hard were asked in this test.

Q1. What is the minimum number of planes required to go around the world?
Ans. 
The minimum number of planes required to go around the world is one.
• One plane can fly around the world without needing to stop.

• The plane can refuel mid-air or carry enough fuel for the entire journey.

• Examples: Non-stop flights like the Boeing 787 Dreamliner or Airbus A350 can circumnavigate the globe with one plane.
Answered by AI
Add your answer

Round duration - 60 minutes
Round difficulty - Easy

Technical Interview round with questions based on data structures and algorithms. Questions about previous projects done and my roles on it and my leadership capabilities. Few technical questions from Threads and multi-processing.

Q1. 
Search in a Row-wise and Column-wise Sorted Matrix Problem Statement
You are given an N * N matrix of integers where each row and each column is sorted in increasing order. Your task is to find the positi...read more
Ans. 
Given a sorted N * N matrix, find the position of a target integer 'X'.
• Start from the top-right corner of the matrix and compare the target with the element at that position.

• Based on the comparison, move left or down in the matrix to narrow down the search.

• Repeat the process until the target is found or the search goes out of bounds.

• Return the position of the target if found, else return {-1, -1}.
Answered by AI
Add your answer
Q2. 
Rectangular Numbers Problem Statement
Ninja has a number 'N'. Your task is to generate a pattern where the outer rectangle is filled with the number 'N', and as you move inward, the numbers decrease conse...read more
Ans. 
Generate a pattern with outer rectangle filled with number 'N' and decreasing consecutively inward.
• Start by filling the outermost rectangle with the number 'N'.

• Decrease the numbers consecutively as you move inward towards the center.

• Continue this pattern until you reach the center of the rectangle.
Answered by AI
Add your answer

Round duration - 60 minutes
Round difficulty - Medium

DSA based questions were asked in this round. Questions on implementation of Linux directory structure were also asked.

Q1. 
Binary Array Sorting Problem Statement
You are provided with a binary array, i.e., an array containing only 0s and 1s. Your task is to sort this binary array and return it after sorting.
Input:
 The fir...read more
Ans. 
Yes, the binary array sorting problem can be solved in linear time and constant space using a single traversal.
• Use two pointers approach to swap 0s to the left and 1s to the right.

• Maintain two pointers, one for 0s and one for 1s, and swap elements accordingly.

• Example: Input: [1, 0, 1, 0, 1], Output: [0, 0, 1, 1, 1]
Answered by AI
Add your answer
Q2. 
Next Greater Element Problem Statement
You are given an array arr of length N. For each element in the array, find the next greater element (NGE) that appears to the right. If there is no such greater ele...read more
Ans. 
The task is to find the next greater element for each element in an array to its right, if no greater element exists, return -1.
• Iterate through the array from right to left and use a stack to keep track of elements.

• Pop elements from the stack until a greater element is found or the stack is empty.

• Store the next greater element for each element in the output array.
Answered by AI
Add your answer
Q3. What is the difference between Binary Search Trees (BST) and Tries?
Ans. 
BST is a binary tree structure where each node has at most two children, while Tries are tree structures used for storing strings.
• BST is used for searching, inserting, and deleting elements in a sorted manner.

• Tries are used for storing and searching strings efficiently.

• BST has a hierarchical structure with left and right child nodes.

• Tries have nodes representing characters, forming a tree-like structure for strings.

• Exa...read more
Answered by AI
Add your answer

Round duration - 60 minutes
Round difficulty - Easy

This was a technical round. Questions about previous projects and current one were asked. I was also asked about aptitude problems from the first round and how I understood and approached towards solution?

Q1. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard without threatening each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not threaten each other.

• Generate valid configurations recursively and backtrack when a solution is not possible.
Answered by AI
Add your answer
Q2. 
Form a Triangle Problem Statement
You are provided with an integer array/list ARR of length N. Your task is to determine if it is possible to construct at least one non-degenerate triangle using the value...read more
Ans. 
Check if it is possible to form a non-degenerate triangle using the sides provided in the array.
• Check if the sum of any two sides is greater than the third side for all combinations.

• If any such combination exists, return true; otherwise, return false.

• Handle multiple test cases as per the constraints provided.
Answered by AI
Add your answer

Round duration - 30 minutes
Round difficulty - Easy

Behavioral questions and team skills were discussed in this round.