That's how I thought of it when I was studying leetcode, and that's the advice I give to other people when they ask how I got my job. Each leetcode solution was another tool in my toolbox. The more tools you have, the easier it will be to put two things together for a larger solution, or to modify a tool to fit a new problem.

I understand the resistance to flash cards as rote memorization without being able to build upon them, I think that's a cogent criticism. At the same time I think some people will be able to take advantage of this to build their toolbox.

And as a minor note, I personally love when people can name an algorithm or concept. There was one interview that I think I completely failed, but I was able to name (but not write out) a concept. I actually incorrectly name dropped Hamming distance, when it was actually the Levenshtein distance, but I was able to diagram the concept behind it. I passed that interview (to my tremendous surprise), and I think the name drop and the simple diagram helped.