Fourkites Software Developer Intern Interview Questions and Answers

There were 3 questions in the online assessment.

1 - Binary Search
2 - DP
3 - Graphs

Q1. Implement a persistence stack with constant time operations
Ans. 
Implement a persistence stack with constant time operations
• Use a combination of a stack and a hashmap to achieve constant time operations for push, pop, and get operations

• Maintain a stack to store the elements and a hashmap to store the index of each element in the stack

• When pushing an element, add it to the stack and update its index in the hashmap

• When popping an element, remove it from the stack and also remove its i...read more
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Q1. Median of two sorted arrays and OOPs basics
Ans. 
Finding the median of two sorted arrays and discussing OOPs basics
• To find the median of two sorted arrays, merge the arrays and then calculate the median

• OOPs basics include concepts like encapsulation, inheritance, polymorphism, and abstraction

• Example: Median of [1, 3] and [2] is 2.0
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Round duration - 100 Minutes
Round difficulty - Hard

**Criteria:
8 CPI or Above (only CSE, MnC). All students irrespective of history of backlogs or current backlogs were considered if they satisfied the CPI criteria.

It was first round..
This round was the Online test which was around 1 Hour 40 Minutes long(don't remember exact time).

Timing from 19:00 to 20:40
Environement was comfortable.
Hackerrank is a good platform for online tests.

All questions were new for me, So cant give any links.

Q1. Minimum Removals
You have been given an array/list "ARR" consisting of 'N' integers. You have also given an integer 'K'.
Your task is to find the minimum number of elements that...read more
Ans. Recursion
The key observation here is that the best way to remove an element from the array is to remove the maximum or minimum element from the array. There are two possible ways of removal, either we remove the minimum element or the maximum element.
Now, the idea is to use recursion to reduce the big problem into several small subproblems. 
 
Here is the algorithm :
1. We sort the array in ascending order.
2. We will ...read more
Answered by CodingNinjas
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Q2. Minimum Number Of Stabs To Kill King
You are given the health of the king as an integer 'N'. You need to find the minimum number of stabs to kill the king. The king dies if the health becomes 0.
...read more
Ans. Recursion
Let’s try to do this problem using recursion, as the problem follows optimal substructure property. That is from any particular value say ‘X’, there are limited possible transitions that you could make.
 
1. If the value of ‘N’ is equal to 1, then we can use only the first kind of stab to kill the king, i.e. do -1 to reduce the health to 0, and the king shall die.
2. Base Case for recursion is when current health ...read more
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Q3. Minimum time
There are ‘N’ junctions connected by ‘M’ bi-directional roads. At most, one road is present between any pair of junctions. There is no road connecting a junction to itself. The travel time for...read more
Ans. Depth First Search
This approach will use DFS(Depth First Search) to make a recursive function in which we pass the currCost, which is the current cost. If the light is not green when we reach that junction, we have to add the waiting time in currCost. After that, we will call the recursive function on all the adjacent unvisited junctions by incrementing the currCost with the weight of the edge. We will maintain a vari...read more
Answered by CodingNinjas
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Round duration - 75 Minutes
Round difficulty - Medium

This was an Online F2F Technical Round conducted on zoom. Interviewer shared codepad link and you were asked to code and pass sample test case given by interviewer. Only one question(coding) was asked(More follow questions).
Interviewer was really helpful..

Q1. XOR Query
Assume you initially have an empty array say ‘ARR’.
You need to return the updated array provided that some ‘Q’ number of queries were performed on this array.
The queries are of two types:
...read more
Ans. Brute Force
Approach:
• It is a brute force approach where we will create an empty array initially of size 10^5 + 1.
• Now, whenever we have a query of type 1 we will insert the value of VAL in the array. And when the query of type 2 comes then we will iterate through our array and perform an XOR operation with VAL to every value present in our array.
• Finally, we will return our array.
 
Algorithm:
• Create an array ans.
• Now it...read more
Answered by CodingNinjas
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Round duration - 90 Miinutes
Round difficulty - Medium

Again pattern was same(Zoom video call and I was asked to code and 1 question was there(+Follow up)).
Timing was afternoon time around 13:00

Q1. Scramble String
You are given an integer ‘N’ and two strings ‘S’ and 'R' each having size = ‘N’. You can scramble the string ‘S’ to obtain string 'R' using the following operations:
1. If...read more
Ans. Recursion
• Since there are many possible combinations in which the strings can be scrambled the only way is to use recursion with memoization to calculate the answer.
• The main idea is to divide the string 'S' into two substrings with length ‘K’ and ‘LEN - K’, where ‘LEN’ is the length of the original string 'S', and check recursively if the two substrings X = S[0….K - 1] and Y = S[k… LEN - 1] form some scramble to generat...read more
Answered by CodingNinjas
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Round duration - 60 Minutes
Round difficulty - Easy

It was a zoom video call.
In starting 5 minutes, interviewer tried to make me comfortable with him..

Q1. Basic HR Questions
Who is your role model?
Where do you see yourself in 5 years?
Ans. 
Tip 1 : Just have a read of some common HR Questions.
Tip 2 : Never write anything false in your CV.
Tip 3 : After every interview I was asked "Whether I have any question for them".Just ask a question about company. This hows your interest in their firm.
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