Ocrolus East Intern Interview Questions and Answers

2 DSA, 1 SQL, 5 ML MCQ

Q1. Probability Questions
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Q2. Tree Based Models
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Q1. Probability Questions
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Q2. Transformer Architecture
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30 Questions - 90 minutes
Difficulty level - medium

Q1. General Introduction, then cross questions on projects mentioned in resume. Discussion on interest and my field of interest. After that the interviewer tested my coding skills in sql by asking 7-8 question...read more
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Q1. Basic Introduction. Some guesstimate questions. Some questions related to business analysis. Finally he asked me about working of various ML algorithms mentioned in my resume.
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Q1. More of a formal talk. About my family background, my projects, what were my role in them. How do I manage myself while on a project. Finally confirmation on relocation availability.
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Round duration - 90 minutes
Round difficulty - Medium

Timings: it was late night. I started the test at 10 pm

Q1. Partial BST
Given a binary tree with N number of nodes, check if that input tree is Partial BST (Binary Search Tree) or not. If yes, return true, return false otherwise.
A binary search tree (BST) is sai...read more
Ans. 
Method 2 above runs slowly since it traverses over some parts of the tree many times. A better solution looks at each node only once. The trick is to write a utility helper function isBSTUtil(struct node* node, int min, int max) that traverses down the tree keeping track of the narrowing min and max allowed values as it goes, looking at each node only once. The initial values for min and max should be INT_MIN and INT_M
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Round duration - 45 minutes
Round difficulty - Medium

It was the interviw round.
the environment was good.
the interviewer was very nice to me.

Q1. Merge two sorted linked lists
You are given two sorted linked lists. You have to merge them to produce a combined sorted linked list. You need to return the head of the final linked list.
Note:
The give...read more
Ans. 
Merge is one of those nice recursive problems where the recursive solution code is much cleaner than the iterative code. You probably wouldn’t want to use the recursive version for production code, however, because it will use stack space which is proportional to the length of the lists.
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Round duration - 120 minutes
Round difficulty - Medium

The online test was for 2 hrs in which 5 coding questions were asked. 3 questions were pretty easy and 2 were of medium difficulty level. I was able to solve all 5 questions.

Q1. Shortest path in an unweighted graph
The city of Ninjaland is analogous to the unweighted graph. The city has ‘N’ houses numbered from 1 to ‘N’ respectively and are connected by M bidirectional roads. If a...read more
Ans. 
Start BFS traversal from source vertex.
While doing BFS, store the shortest distance to each of the other nodes and also maintain a parent vector for each of the nodes.
Make the parent of the source node as “-1”. For each node, it will store all the parents for which it has the shortest distance from the source node.
Recover all the paths using the parent array. At any instant, we will push one vertex in the path array an...read more
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Round duration - 60 minutes
Round difficulty - Medium

It started with the introduction and then we had a discussion on the projects I had made. He asked for several Backend and Database concepts like locking in DB, sessions, etc as I had mentioned backend internship in my resume. It took around half an hour.

Then he gave me a coding question based on the graph

Q1. Capture region
You are given a matrix having ‘N’ rows and ‘M’ columns. Each cell of the matrix is either ‘X’ or ‘O’. You need to flip all those regions of ‘O’ which are surrounded by ‘X’ i.e. you need to c...read more
Ans. 
I first took some time to think of a solution then told him the DFS as well as BFS approach. Then he made me run through several test cases on the pseudo-code. Once he was satisfied with the approach then I coded it on the editor and ran several test cases which he gave.
Finally, He asked me about the Time-Complexity and Space-Complexity of the code.
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Round duration - 45 minutes
Round difficulty - Medium

Two DSA questions were asked in this round in 45 min.

Q1. Maximum Subarray Sum
Given an array of numbers, find the maximum sum of any contiguous subarray of the array.
For example, given the array [34, -50, 42, 14, -5, 86], the maximum sum would be 137, since w...read more
Ans. Brute Force Approach
1. Create a nested loop. The outer loop will go from i = 0 to i = n - k. This will cover the starting indices of all k-subarrays
2. The inner loop will go from j = i to j = i + k - 1. This will cover all the elements of the k-subarray starting from index i
3. Keep track of the maximum element in the inner loop and print it.
Space Complexity: O(1)Explanation:
O(1) because the extra space being used (looping vari...read more
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Q2. Find Odd Occurrence Element
You are given an array of 'N' elements. In this given array, each element appears an even number of times except one element which appears odd no. of times. Your task is...read more
Ans. Brute force
We will find the frequency of all elements by iterating over the whole array N times. On completion of iteration if the frequency of element is odd. We will return this element else keep on iterating.
1. Let’s say we have a given array ARR and pair sum K.
2. Iterate over ARR[i] for each 0 <= i < N and do:
   1. COUNT=0
   2. Iterate over ARR[j] for each 0 <= j < N and do:
      1. If ARR[i] = ARR[j] then increase COUNT by 1.
   3. If ...read more
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