[onion2k]

"this is a seriously bad way of hiring developers"

We can't reasonably assume that Twitter uses this sort of question in all their developer interviews. We don't have enough data for that. Perhaps this guy was going for a role where solving problems quickly and under pressure was a key requirement. If that were the case, this is pretty much a perfect interview question.

[smsm42]

I have hard time imagining what position, at least if we're talking about software engineering, would require solving abstract toy problems in a timeframe of less than an hour without a chance to ever go back and improve your solution. I'd say it's "did you see this problem before" kind of question. Which means Twitter probably lost a capable and smart hire because he couldn't quickly give a perfect answer to useless puzzle (unless of course he was hired to repair the roof in Twitter's office and solving this puzzle is required for Twitter to survive the rainy season). Hardly a "perfect" way.

[etler]

Twitter interview puzzle creator?

[smsm42]

You can take months to create puzzles, there's no pressure here.

[stefan_kendall]

The problem is that this is a bread and butter ACM problem. Anyone who has competed will know the solution. And biasing for ACM competitors is awful.