FFT，即为快速傅氏变换，是离散傅氏变换的快速算法，它是根据离散傅氏变换的奇、偶、虚、实等特性，对离散傅立叶变换的算法进行改进获得的。它对傅氏变换的理论并没有新的发现，但是对于在计算机系统或者说数字系统中应用离散傅立叶变换，可以说是进了一大步。(FFT, that is fast Fourier transform, is a fast algorithm for discrete Fourier transform. It is based on the odd, even, imaginary, real and other characteristics of discrete Fourier transform, and the algorithm of discrete Fu Liye transform is improved. It does not make new discoveries about the theory of Fourier transform, but it can be a big step for the application of discrete Fu Liye transform in computer system or digital system.
Let x (n) is a complex sequence of N, by DFT transform, either X (m) calculations are N times N-1 times complex multiplication and addition, and a complex multiplication is equivalent to four times the number of multiplication and two real addition, a complex addition is equivalent to two times the number of addition,)