fft混合基算法，c代码实现，可移植混合基的傅立叶变换算法-FFT algorithm of mixed base, c code, portable mixed base of Fourier transform algorithm

附件有三个傅里叶变换的程序，都已测试，他们是可用的。并且程序的每个步骤都有详细的说明，简单易懂。(The attachment has three Fourier transform programs that have been tested and they are available. And each step of the program has a detailed descr iption easy to understand.)