Comment by 3vidence

Honestly in day to day programming I find data types & associated APIs are so so much more important than algorithms.

I would rather work with a flexible data type with suboptimal performance than a brittle data type that maybe squeezes out some extra performance.

Your example of in-place array mutation feels like a good example of such a thing. I feel like there should be a category of interviewing questions for "code-safety" not just performance.