说明：  虽然现在网上的FFT程序很多，但是有的结果是错误的，比如说，经过一次正反变换后，不能得到原来的数列，所以，本人测试了多个程序，提供几个能用的，给大家，希望大家支持！
(Although many online FFT program, but some results are wrong, for example, through a positive and negative change, you can not get the original series, so I tested several programs to provide a few usable for everyone I hope we can support!)