I was applying for the software engineer intern position. This was my first technical interview, lasting 45 minutes.

First, there was a 10-minute discussion about my projects.

Then, I was asked a technical question about prime numbers. The algorithm was provided, so I only needed to implement it, which made it easy. The follow-up question was about performance.

Finally, I had the opportunity to ask my own questions. I learned that at Square, interns are integrated into real teams and work alongside them. It was a pleasant interview.

Find the prime numbers smaller than N. The Sieve of Eratosthenes algorithm is given to implement.

First, start with the first prime, 2. For each identified prime number, mark all multiples of the prime as composite.

Increment the index and check to see whether the number has been marked as composite. If it has not been marked, it is a prime. If it has been marked, it is skipped.

The followup question is about how to improve the performance.