📌 My PhonePe Interview Experience

Introduction

I’m an undergrad studying in my fourth year of engineering in Computer Engineering at Pune Institute of Computer Technology. As per every year, PhonePe visited our college with the golden opportunity of a full-time SDE Role at their prestigious organization. The drive was open to all BE students as long as they fulfilled the criteria for dream companies set by our college TnP Cell. Gritting my teeth, I went into what was a test of sheer resolve and skills.

📢 PPT (Pre-Placement Talk)

We had a Pre-Placement Talk open to all students where they thoroughly discussed the company policies, values, use cases, tech stack, compensation, etc. I jotted down a few notes from the PPT for discussions in later interview rounds, especially the HR round. (Bitter foreshadowing)

Round 1: Online Assessment

• The Online Assessment was held on DoSelect Platform early in the morning at 9 AM.
• The test had 4 questions and 90 minutes to solve all of them with a score of 100 per question.

Problems:

1. In an office of N lanes with desks of only prime lengths, each team is supposed to sit in one lane. The length of the ith lane and the cost of laying one desk in the ith lane are represented by 2 arrays. Find the minimum total cost to complete desking of all N lanes. (Easily solvable with SPF and modular arithmetic.)

2. Rearrange an array of positive integers to maximize the sum of GCDs of adjacent elements in the array. (I managed to pass half the cases with next_permutation. The most optimal approach probably lies in bitmask DP.)

3. Maximize the members in a team where the ith member will only join if ai members have strictly greater power than him and bi members have power less than him. (I couldn’t solve this one; it's likely solvable with binary search on answer.)

4. Find the total number of ways to execute all functions given that they can only be executed if a given function before them was previously executed. (Didn’t get time to look into it much so can’t say.)

I solved the 1st problem completely and the 2nd one partially. 11 people were shortlisted, including me, from the coding rounds for further evaluation.

First Technical Interview Round

It was an offline interview which roughly lasted for an hour. The mode of the interview was pen and paper. The interviewer was rather zealous and obliging. It seemed as if he had tons of experience under his belt. He attempted to put me in vulnerable situations in even the easiest problems a lot.

He started by asking about myself a bit. Then, he asked if I had worked on a project in any database, to which I agreed and told him about one in PHP and SQL. We then discussed my project during my summer internship and my overall experience regarding the same.

He later insisted on continuing the interview with Problem Solving / Data Structures questions, to which I willingly agreed.

Questions:

1. Merge Two Sorted Arrays

   • Given two sorted arrays of integers, merge them into a single sorted array. (Easily done with two pointers.)
   • Then he scaled the problem to 10 arrays. I suggested using a hashmap, 10 pointers, priority queue, or a binary search tree.
   • Note: He bugged me a lot with even the smallest and unorthodox corner cases not being included in my pseudocode. So always start with requirement gathering and look out for corner cases when approaching interview questions.

2. Find the Pair with Maximum Product

   • Given an array of integers, find the pair with maximum product. (Easily solvable with 4 pointers.)

He discussed a lot over the complexities of these approaches and if it is possible to improve them further, even over average cases. Then, he asked if I had any questions for him, to which I responded by asking a few regarding use cases of Contact Graphs in PhonePe.

6 people, including me, made it to the second round.

Second Technical Interview Round

It was an offline interview which roughly lasted for 45 minutes. The mode of the interview was pen and paper. The interviewer was a bit timid but knew a lot about problem-solving and competitive programming.

He started by asking me which direction I wanted the interview to go (either coding or development), to which I responded with coding.

Then, he asked me about my favorite data structure. MY FIRST MISTAKE! I responded with graphs, hoping for an extra impression. He asked me stuff about Disjoint Set Union and its complexities. I did manage to answer but it shook my confidence and resolve a lot in the end.

Questions:

1. Number of Ways to Cut a Land

   • Given a land with N x M plots, there are T known treasures buried in some of them. You have K sons.
   • In one operation, you can either cut the land vertically and give all plots to the left of the cut to one of your sons or cut the land horizontally and give all plots above the cut to one of your sons.
   • Basically this: Leetcode Problem
   • MY SECOND MISTAKE! I perceived the problem to be harder than it ever was. I couldn’t answer further.

2. Painters Painting a Roof

   • Alice and Bob are two painters painting a roof of N x M cells.
   • Alice paints the roof horizontally in A1, A2, ..., AN and Bob paints it vertically in B1, B2, ..., BM.
   • To find the bad cell count: I answered with a solution in binary search with O(N log M) Complexity.

3. Array Splitting Problem

   • Literally this problem but without the circular arrangement part.
   • I answered with an O(N) solution by sorting and splitting the array.

4 people were selected from this round. Unfortunately, I got rejected.

🎯 Conclusion

I got rejected, but the experience felt worth the hassle. Thanks to Competitive Programming, I made it as far as I could. The drive was great overall, my skills, luck, and resolve weren’t enough, and the best candidates got their well-deserved roles.