说明：  编写一个matlab函数用一个N点离散傅里叶变换同时计算两个N点实序列的离散傅里 叶变换，并将结果与直接使用两个N点离散傅里叶变换计算出来的结果进行比较
(Write a matlab function with an N point discrete Fourier transform and calculate actual sequence of two N point discrete Fourier transform, and the results with the direct use of two N point Discrete Fourier Transform calculated results are compared)