离散傅里叶变换(Discrete Fourier Transform)

By Long Luo

todo

https://www.geeksforgeeks.org/discrete-fourier-transform-and-its-inverse-using-c/
https://www.geeksforgeeks.org/how-to-compute-a-discrete-fourier-transform-coefficients-directly-in-java/
https://github.com/graetz23/JWave/blob/master/src/jwave/datatypes/natives/Complex.java
https://www.nayuki.io/page/how-to-implement-the-discrete-fourier-transform