The initial call was from the recruiter, who asked me about my background and a quick pop quiz (true or false) of 10 tech questions. I answered 9 of them correctly.

Next, I had a telephone interview with a Google engineer.

The initial part of the interview focused on the group, their product, and my knowledge of the market surrounding the product.

The next part was technical, requiring me to code to check if a Sudoku square is valid. I managed to answer correctly, coding in C. The interviewer was professional and asked me to use the language of my choice.

Write code to check the validity of a Sudoku square.