Radix sort revisited

Around a year and a half ago I wrote an article on the perils of relying on big-O notation, and in it I focused on a comparison between comparison-based sorting (via std::sort) and radix sort, based on the common bucketing approach.

Recently I came across a video on radix sort which presents an alternate counting-based implementation at the end, and claims that the tradeoff point between radix and comparison sort comes much sooner. My intuition said that even counting-based radix sort would still be slower than a comparison sort for any meaningful input size, but it’s always good to test one’s intuitions.

So, hey, it turns out I was wrong about something. (But my greater point still stands.)

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The danger of big-O notation

A common pitfall I see programmers run into is putting way too much stock into Big O notation and using it as a rough analog for overall performance. It’s important to understand what the Big O represents, and what it doesn’t, before deciding to optimize an algorithm based purely on the runtime complexity.

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