说明：  本代码实现 Cooley-Tukey 蝶形算法计算复数域的一维快速傅里叶变换。非迭代方式，节约内存，执行速度快。要求数据个数为2的整幂次方，符合语法规范，可直接使用。
(In this code, Cooley Tukey butterfly algorithm is implemented to calculate one-dimensional fast Fourier transform in complex field. Non iterative, memory saving, fast execution. It is required that the number of data is an integer power of 2, which conforms to the syntax specification and can be used directly.)