McKinsey & Co. Interview Experience for SDE

McKinsey visited our college in August 2022 for the software engineer role.

Round 1: The first round consisted of 2 coding questions and 2 SQL queries. The questions asked were:

• Coding Question 1 – Slight variation of 0/1 knapsack where we had to return maximum quantity instead of value.
• Coding Question 2 – Medium level bit manipulation question.
• SQL queries – One was easy, and the other one was medium.

I solved all the questions. The cutoff was to solve all the questions. I got shortlisted for the next round with around 300 students. The next round was a code pair round.

Round 2: This round was a code pair round. One of the McKinsey employees will accompany you throughout the round; it was happening in batches in campus labs. The team gave me one DP question to me:

•  Question: There are several cities in a row, and two bus lines go between them. They both visit all cities in order, but one may take longer than the other to go between any two cities. Starting or moving to the blue line takes a certain amount of extra time. No spare time is required to begin on or move to the red line. Determine the minimum cost to move from the first city to each city.

Proposed Solution: First, we had to tell the logic to the personnel assigned, and then the executive would ask us to write a pseudo-code; once he approves it, we can start coding the solution. So, I started initially by giving a recursive solution (Top-down), I had to draw the entire recursive tree, and after the interviewer asked me the time complexity, I told him it would be exponential, and after that, he told me to improve the complexity, I said we can use dynamic programming to reduce the complexity. I quickly told him, and he told me to code the solution; I had around 40 minutes on the clock. I wrote the answer initially; 10/15 test cases passed, and I called the interviewer to ask for feedback; he said I was missing some base cases; I worked for another 5 minutes and could figure out all the test cases passed. The interviewer told me to add comments and leave the lab.

Round 3: The third round was a technical interview. The shortlists for all three batches totaled 45 students.

• The interviewer reviewed my resume and asked me about my projects and OOPs questions.
• After the OOPs questions, he asked me to write a medium-level SQL query.
• Next, he asked me to give a high-level design for a given problem.
• He asked me some DSA questions, like searching in a rotated sorted array. I gave him all the approaches, from brute force to the most optimized.
• I got called for the next round within 5 minutes!

Round 4: This was the final round with the CTO of McKinsey India hub.

• Computer fundamentals were the focus of this round.
• First, he told me to rate myself in subjects like OOPs, OS, DBMS, CN, DSA, and DAA.
• He started with OOPs and asked me about the Multiple Inheritance – Diamond problem, Polymorphism.
• Then he asked me from DBMS about various anomalies, minimal cover, and functional dependencies.
• Next, he asked me about spanning trees; I explained and talked about MSTs and algorithms to find them using prims and Kruskal’s.
• After this, he started asking me questions about my projects; since my projects were from a machine learning background, he tested me on various ML algorithms.

Verdict: 10 people were selected, and I was one of them and was offered INT + FTE. One difference from other companies was that after every round the McKinsey team used to brief all the selected students on what they were expecting from us, giving us some sense of direction to frame our answers. Overall, it was a good experience.