Walmart Interview Experience

Walmart Global Tech came to our campus in the month of August to interview students for the position of Software Development Engineer.

After a CGPA-based shortlisting, around 250 students were chosen to participate in the Online Assessment.

The first round was an Online assessment that was of medium to hard difficulty level questions.

Online Assessment:

The platform to conduct online assessment was HackerEarth, and the time duration was 1 hour precisely.

• Total of Ten technical MCQs, belonging to  Networks, OS, DBMS, OOPS, and SQL.
• Two coding questions medium-hard level

Coding Questions:

• You are provided with two strings A and B that are made of only lowercase English alphabets(a,b,c..). Find the number of distinct pairs of ((i,j) and (k,l)) such that the substrings formed by A[i…j] and B[k…l] are equal and the value of the expression j-i+1 is minimum

Solution:

 int Question_Walmart(string A, string B) {

    char frequency[256] = {0};

    for (auto c : A) {

        frequency++;

    }

    int sum = 0;

    for (auto c : B) {

        sum += frequency;

    }

    return sum;

}

• Given an array which has N items a1,a2,a3,a4..so on .and, two integers Kand X. Where K denotes the maximum number of jumps you can take in the either of the direction that is from position i, You can jump to position j in one step only if the condition of abs(j-i) <= K and 1<=j<=n are satisfied..
  Jumping from i to j  will cost X amount, if a[i] = a[j].
  Find minimum cost to reach the position an from position a1.
   int question_walmart(vector &arr, int n, int k, int x)

{

    vector dp(n, INT_MAX);

    dp[0] = 0;

    for (int itr = 0; itr < n; itr++)

    {

        for (int j = max(0, itr - k); j <= min(n - 1, itr + k); j++)

        {

            if (dp[j] > dp[itr] + (arr[j] == arr[itr] ? 0 : x))

            {

                dp[j] = dp[itr] + (arr[j] == arr[itr] ? 0 : x);

            }

        }

    }

    return dp[n - 1];

}

Students with one entire and one partial solution correct also advanced to the next round after passing all test cases for both Problems..

For the next round, 31 people were Selected.

Round 1(Techincal Interview Round 1): 50-55 min

• This round was an Technical interview round conducted over Zoom call.
• The interviewer started by first introducing himself, he was an SDE-3(Team Backend) and had almost 10 years of experience in the Software Engineering field and was working with Walmart for quite long time. I was not asked to code any of the problems in this round, it is focused more on the core CSE subjects.
• Later I was asked introduce myself and then we went straight to the technical questions based on Core CSE subjects.
• He gave me a  link to google docs which I have to use to explain the answers to the interviewer.
• There were 2 machines and the first machine wants to send an message to the second machine. Explain how the communication will take place. I explained to him everything about the Open Systems Interconnection and TCP/IP models, the working of the each layer in transmitting data from one node to other, and The 3-way handshaking protocol to help establish connections. He was quite satisfied with my explanations.
• Was about the implementation of the STL called Unordered set, he asked me if I have an unordered set consisting of N numbers, and how will I modify it to an ordered set without using any of the sorting algorithms. I told him the explanation that we can make an BST of the provided unordered set and then do the inorder traversal of the binary search tree to get the ordered set of the given elements. I explained my complete approach on the shared google doc file.
• He was quite satisfied with the explanation and didn't asked me to code it on the system.
• You are provided with an sorted array, with one repeating number, Find that number. I gave him the first brute force solution in O(n) TC, After which he asked me to make my solution a bit more complex as of now(yes, more complex!!). It was odd and interesting at the same time for an interviewer and even for the candidate to ask to make the solution more complex, I must say that the interviewer was very polite and had immense knowledge of the topic later we had a good discussion on the same.
• Various questions were asked on the concepts like Paging and Segmentation and Threading. The interview went for about 55 min, at the end he asked to me that whether I had any questions for him to ask, and I asked about his all of the day-to-day responsibilities at Walmart as a Data Scient. , which he answered in a very informative way.
• 25 students in total were selected for the upcoming round.

Round 2(Technical Interview 2): 1.5 hour

Conducted over a zoom Call. The interviewer was an Senior Data Scientist at Walmart and he asked me initially that this is an coding round. Before moving to the coding questions, we had good discussion about the projects I had made since my resume was based on Data Science.

A few questions that were asked are,

• Why is LSTM better than the simple RNN, explain? Explained all the important points including the vanishing gradient problem. Also the mathematics behind it.
• Why did you have used Random Forest Algorithm in one of your major projects? Explained all the pros of the Random Forest Algorithm, its complete working, And how is it different from an decision tree algorithm.
• What is  the relative feature importance and partial dependent plots, Explain? I Had used it in one of the my projects, and so I explained it to him and he was satisfied with my explanation.
• Explain the bias-variance trade-off and how can you use Random Forest to solve personalization problems, Explain? Then we moved on to the major point of this round, The coding questions, he asked me to open any IDE and code.
• Pattern printing question: Problem Link
  Identified that it was an pascal's triangle, then explained him the logic and later, he asked me to code the solution while sharing my ide screen.
• The code ran successfully, and he was completely satisfied.
• Next question was, Finding the loop in given linked list:Problem Link. 
  He didn't asked me to code this, only needed to explain the brute approach to him, I gave him the brute force approach, and  then I used MAPS to reduce the Time complexity, and in the end, he was quite satisfied with the O(n) time complexity and space complexity of O(n) (PS: We can solve it in O(1) space as well, Peace!)
• Write an function that have an equal probability for printing YES and NO. I Gave him the idea about the rand() functions in C++, and then followed up by altering the probability for printing YES to be 25% and later 10%. I Suggested some tips in the rand() function, and he was quite satisfied with the answer.
• The interview went for about 1 hour long, and at the end he asked me whether I had any questions, I asked him about his day-to-day responsibilities at Walmart as an Data Scientist, to which he answered in a very informative and polite manner, and the interviews ended.

Tips: Make sure you can explain for everything that you have written in your resume because the interviewer will go deep into the tech stacks and points of your projects and internships.

Round 3(Hiring manager Round): 1 hr

• 
  I was asked to wait on the same time after my technical round ended and about 10 minutes later, I had this round the HR round, I was informed that it was my final round of the interview series.
• The interviewer first asked my introduction, then asked two questions based on my Resume, My experience about winning the first hackathon. Why did I choose to do the ML certification?
• He asked me what is the most important quality in a leader.
• After That we had a long discussion about Walmart, Working principles, and innovations at Walmart, also any recent technology on which Walmart is working on currently.
• He also asked me some technical questions as well, like what do I understand about Cloud, and What is the difference between a Public and a Private Cloud?
• Later, I asked him about various teams which were working at the Walmart.
  All in all, we had a very good discussion over it. The interview went for about an hour or more I guess, he then wished me Good luck and waited to look out for any updates regarding the results from the placement cell.
• Results were announced the very next day, 16 students were selected as Full Time, and 7 were selected as interns which could be converted to Full time based on performance. 

I was selected as one of the Full time.

You can check out more such Walmart interview experience & also interviews for other companies like Amazon, Google, Microsoft, to prepare for your own interview.