Summary
I had a phone screen with Airbnb where I was tasked with implementing the Connect Four game logic, focusing on well-structured code and handling game states like full columns and winning conditions.
Full Experience
During my phone screen at Airbnb, I was presented with the challenge of implementing the classic game Connect Four. The interviewer provided a clear problem statement, outlining the game rules, input format, and expected output for displaying the grid and handling various game states. The emphasis was on writing well-structured code rather than focusing purely on immediate optimizations, with the possibility of discussing further optimizations as follow-up.
Interview Questions (1)
Connect Four is a two-player connection board game. The players choose a color and then take turns dropping colored tokens into a seven-column, six-row vertically suspended grid. The pieces fall straight down, occupying the lowest available space within the column. The objective of the game is to be the first to form a horizontal, vertical, or diagonal line of four of one's own tokens. - Wikipedia
The input is a list of columns played successively by the two players. The output is to display the Connect Four grid associated when the game finishes.
If a winning state is reached or if a wrong move is played, the game should stop even if there are still columns in the list. In that case, only the tokens that have been played should be displayed in the grid.
The goal is to write code that is well-structured, rather than a solution that is too complex. Optimisation may be discussed during follow-up questions.
Examples:
Input (column full):
[2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]Output:
| | |X| | | | |
| | |0| | | | |
| | |X| | | | |
| | |0| | | | |
| | |X| | | | |
| | |0| | | | |
In this example, we start playing with the 0 token. The 7th item of the input is invalid because the column is already full.
Summary
I applied for an SSE role at Airbnb and was rejected after completing an online assessment followed by two coding rounds and a system design interview.
Full Experience
I initiated my application through the Airbnb career portal and was subsequently contacted by an Airbnb recruiter after a few weeks. The initial screening involved an online assessment, which was a Hackerrank test comprising a single graph-based problem. Unfortunately, I don't recall the exact problem statement, but my solution resulted in a Time Limit Exceeded (TLE) error for one test case, although it passed the others.
Following the online assessment, I was invited for further interview rounds. These consisted of two coding rounds, each 45 minutes long, and one system design round, which lasted approximately 60 minutes.
Round 1 (45-min): This round focused on finding the minimum window in a string containing all characters from a given pattern. I initially suggested a brute force approach. With some hints from the interviewer, I managed to develop a more optimal solution, though my code still contained a few bugs.
Round 2 (45-min): The second coding round presented a problem similar to a sliding puzzle. I began with a DFS-based approach, which was suboptimal for this particular question. I then transitioned to a BFS-based approach, which proved to be a better solution. The interviewer pointed out a couple of errors in my code during this round.
Round 3 (System design, 1 hr): For the system design round, the problem involved designing a system to handle current weather data. The scenario was that I would receive weather data at periodic intervals from multiple sub-stations across a country. Each sub-station would provide weather data for its specific region in a defined format. The task was to build a system capable of fetching historical data and providing future weather predictions for a given region. The interviewer was primarily interested in a high-level design. I apologize if the question seems vague; I may have forgotten some of the finer details.
Verdict: I was ultimately rejected due to my performance in the coding rounds. The feedback indicated that they expected optimal solutions with minimal hints.
Interview Questions (3)
Design a system to collect current weather data from multiple sub-stations, store historical data, and provide future weather predictions for given regions. Focus on a high-level architecture.