编写一个MATLAB函数，实现快速卷积算法，给出一个实例。用一个N点离散傅立叶变换同时计算两个N点实序列的离散傅立叶变换。-The preparation of a MATLAB function, fast convolution algorithm, given a case in point. With a N-point discrete Fourier transform at the same time calculation of the two N-point real sequence of discrete Fourier transform.