I'd put Fourier transforms on the list of algorithms that are extremely useful to know. (Well, not exactly the algorithm itself as much as the concept.) Many th

I'd put Fourier transforms on the list of algorithms that are extremely useful to know. (Well, not exactly the algorithm itself as much as the concept.) Many things make a lot of sense if you understand Fourier transforms, such as computer graphics, audio processing, signal processing, image processing, data analysis, filtering, and electronics. But Fourier transforms get hardly any attention on HN.