一直挺想学FFT。
1.n次单位根
http://wenku.baidu.com/link?url=x4Ot-WwMJOUCzs8soBnlVTQzlFJy0evAuVJYVG4Pe68ASMgws9LR1r7i02QZnx94JDSyoHNSb0s4dFObMyeTClbiNssF2dFqg5GZ0NVATJ_
2.FFT
http://blog.csdn.net/iamzky/article/details/22712347
原文:http://www.cnblogs.com/fighting-to-the-end/p/5912576.html