Fastenal Software Developer Intern Interview Questions and Answers

Q1. How set is implemented?
Ans. 
A set is implemented as a data structure that stores unique elements with no specific order.
• A set does not allow duplicate elements.

• Sets are commonly implemented using hash tables or binary search trees.

• Examples of set implementations include HashSet in Java and std::set in C++.
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Q2. How unordered set is implemented?
Ans. 
Unordered set is typically implemented using hash tables.
• Uses hash tables to store elements with unique keys

• Provides constant time complexity for insertion, deletion, and lookup operations

• Does not maintain any specific order of elements
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Easy level Basics were asked

Stacks queue leetcode easy level

Q1. Basic project discussion
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Q2. Skills used in project
Ans. 
Used skills include Java, SQL, Spring Boot, RESTful APIs, and Git.
• Java programming for backend development

• SQL for database management

• Spring Boot for creating web applications

• RESTful APIs for communication between systems

• Git for version control
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Round duration - 90 minutes
Round difficulty - Medium

Timing was late evening. Platform was good.

Q1. 
Largest Cycle in Maze Problem Statement
Given a maze represented by 'N' cells numbered from 0 to N-1, and an array arr of 'N' integers where arr[i] denotes the cell number that can be reached from the 'i'...read more
Ans. DFS
The idea is to do a depth-first search to find all the cycles which are formed and calculate the length of the largest cycle. We are treating the array as a graph of directed edges. Whenever we get into any of the cells in the cycle, using dfs we will visit all the subsequent cells in the cycle. Out of all the cycles, we will return the cycle of maximum length.
The steps are as follows:
• Initialize a boolean array ‘vis...read more
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Q2. 
Rat in a Maze Problem Statement
You need to determine all possible paths for a rat starting at position (0, 0) in a square maze to reach its destination at (N-1, N-1). The maze is represented as an N*N ma...read more
Ans. Bactracking
Approach: We can start the traversal of the paths from the rat’s starting position, i.e. (0,0) keeping track of the visited cells during the traversal. We will recursively go through all the paths possible until the last index of the grid (destination) is reached, and add the path information using which the rat successfully reached the end.
 
Algorithm is as follows:
 
1. Take the starting position of th...read more
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Round duration - 65 minutes
Round difficulty - Hard

Timing (6pm - 8pm)
Environment was user friendly
As usual the online round had three coding questions and 20 MCQs. This was a pretty easy round and it’s duration was 65 minutes. The round consisted of questions from various domains like Algorithm, Data Structure, Operating System and Aptitude.

Q1. 
Determine Count of Good Triplets
You are given two arrays ARR1 and ARR2, containing N and M elements respectively. There are two types of 'good triplets' that need to be identified in these arrays.
Type ...read more
Ans. Brute Force
A simple method is to generate all possible triplets and check for each triplet if the triplet follows the given conditions.
Our approach will be to traverse through ARR1 and in each iteration, we will consider all pairs from ARR2 and check if the element from ARR1 and the pair from ARR2 follow the given conditions of type 1 triplet.
To obtain type 2 triplets, we will traverse through ARR2 and we will consider...read more
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Q2. 
Split the String Problem Statement
You are given a string str consisting of N lowercase alphabets. Your task is to determine if it is possible to divide the string into three non-empty substrings such tha...read more
Ans. Brute-force
The idea here is to check all possible ways to divide a string into 3 substrings and check if there is a string that is a substring of the other two parts. We can divide a string into 3 non-empty substrings:
• A non-empty prefix
• A non-empty suffix
• And a non-empty middle string that is between the ending point of the 1st string and starting point of the 2nd string.
 
Algorithm:
 
• Run a loop from i = 1 to ‘N’...read more
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Round duration - 40 minutes
Round difficulty - Medium

Q1. 
Check if Two Trees are Mirror
Given two arbitrary binary trees, your task is to determine whether these two trees are mirrors of each other.
Explanation:
Two trees are considered mirror of each other if...read more
Ans. Recursive Approach
Traverse the tree T in preorder fashion and treat every node of the given tree T as the root, treat it as a subtree and compare the corresponding subtree with the given subtree S for equality. For checking the equality, we can compare all the nodes of the two subtrees.
 
For two trees ‘S’ and ‘T’ to be mirror images, the following three conditions must be true:
1. Their root node’s data must be the sam...read more
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Q2. 
Snake and Ladder Problem Statement
Given a 'Snake and Ladder' board with N rows and N columns, where positions are numbered from 1 to (N*N) starting from the bottom left, alternating direction each row, f...read more
Ans. BFS
We will use Breadth-First Search to find the shortest path from cellNumber 1 to cellNumber N*N.
1. We will maintain a queue of cellNumber where the front of the queue will always contain a cell which can be reached by minimum dice throw from starting cell (cellNumber = 1).
2. Create a minDiceThrow array of size N*N initialise it with the maximum value (INT_MAX)
3. Start with pushing cellNumber 1 and updating minDiceThrow[1] = 0...read more
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