Procol Interview Experience (On-Campus)
Online Test: 9th Sept 2020
Interview: 10th Sept 2020
Written Test: First of all 230 students were selected by Procol, Gurugram from a pool of 600+ eligible students on basis of resume.
The online test consists of 2 sections:
21 MCQ’s: MCQ’s were based on concepts of networking, operating systems, MySQL and oops.
3 coding questions, coding questions:
- Concatenate n strings from the index where a vowel occurs.
Input Strings: abcde, bcdef, fgkl, dseiou Output String: abcdeefeiou
The simple bruteforce O(n) approach worked (where n is the total length of all the strings combined). I did this question.
- Minimum changes required to make all the numbers in an array prime.
I solved this question using Digit DP. Idea was to calculate all the primes using a sieve then make 2 arrays which defined the distance of a particular number from the left and right of a prime number. Now for every query simply the minimum of both arrays was our answer.
- Given an array A of N numbers, you have to perform B operations. In each operation, you have to pick any one of the N elements and add the original value(value stored at index before we did any operations) to its current value. You can choose any of the N elements in each operation.
Perform B operations in such a way that the largest element of the modified array(after B operations) is minimised. Return an integer corresponding to the minimum possible largest element after K operations.
Input: A = [1, 2, 3, 4] B = 3 Output: 4
Explanation: After the 1st operation the array would change to [2, 2, 3, 4] After the 2nd operation the array would change to [3, 2, 3, 4] After the 3rd operation the array would change to [4, 2, 3, 4]
A : [ 8, 6, 4, 2 ] B: 8 The expected returned value: 12
I was not able to solve this problem completely and 2 out of 3 test cases were run.
23 out of 230 students were selected for the Virtual Interview process on 10th Sept.
Interview: There were 2 rounds of interviews and both were technical.
Tips: Please have a good internet connection, broadband is preferred as I connected with my cellular 4G but the voice of the interviewer was breaking, and we had to reschedule the interview.
- It started with a discussion of my projects and internship.
- How to find if a number is the power of 2 or not. First I told the brute-force approach then told the bit manipulation approach of x&(x-1) must be 0 to be a power of 2.
- Are you familiar with the stack? I said Yes.
- Describe it and what are the stack operations? Explained
- How to implement stack? I explained using the linked list approach.
- Why can’t we use arrays? Explained the static nature of arrays
- On the further discussion on implementation with the linked list, we found that pop operation would be costly. So how to make it efficient? I suggested the reverse linked list method, to make a stack using a reverse linked list. He was convinced.
- Do you know SQL? Yes sir.
- What are the joins? Explain left outer join. Explained
- What is context Switching? I explained something, but I was sure I am wrong, so told I am not able to remember.
- Given an unsorted array, find two pairs such that the sum of the pairs is k. First I gave a brute-force approach of O(n^2). Then told a better approach by hashing.
- Given a sorted binary array whose size could be as big as 10^14. We don’t know the size of the array and also we cannot find it. Find the occurrence of first “1” in the array.
I stumbled on this question as we cannot find the size or we could have done a simple binary search. So I came with a redefined binary search where first we can check every 100,000th number can see if it is 1 or not, If it is then we are sure our first 1 is this or on the left part of the array so simply do a binary search from this index to 100,000 indexes left.
- Can we optimize it?
After some thinking, I told to instead of keeping a gap of 100,000 we could use an exponential gap. Like for example, I suggested taking the 2^i gap which increases readily thus we can reach our 1st “1” faster. Accounting it to O(logN) algorithm. He was impressed.
- What is Normalization in DB,S? Answered
- What is LRU cache? How to implement it? Any real-life example where LRU is used? Answered
- Swap two numbers with taking additional 3rd variable? I suggested a method using bit manipulation.
x = y ^ x^ (y=x);
He told me to run it using some test cases including negative numbers and it executed successfully.