Write a program to find 100 largest numbers out of an array of 1 billion numbers

Question

I recently attended an interview where I was asked \"write a program to find 100 largest numbers out of an array of 1 billion numbers.\"

I was only able to give a br

Answer 1

I realized that this is tagged with 'algorithm', but will toss out some other options, since it probably should also be tagged 'interview'.

What is the source of the 1 billion numbers? If it is a database then 'select value from table order by value desc limit 100' would do the job quite nicely - there might be dialect differences.

Is this a one-off, or something that will be repeated? If repeated, how frequently? If it is a one-off and the data are in a file, then 'cat srcfile | sort (options as needed) | head -100' will have you quickly doing productive work that you are getting paid to do while the computer handles this trivial chore.

If it is repeated, you would advise picking any decent approach to get the initial answer and store / cache the results so that you could continuously be able to report the top 100.

Finally, there is this consideration. Are you looking for an entry level job and interviewing with a geeky manager or future co-worker? If so, then you can toss out all manner of approaches describing the relative technical pros and cons. If you are looking for a more managerial job, then approach it like a manager would, concerned with the development and maintenance costs of the solution, and say "thank you very much" and leave if that is the interviewer wants to focus on CS trivia. He and you would be unlikely to have much advancement potential there.

Better luck on the next interview.