hi,all.I wrote this program to implement the FFT algorithm.Running with wrong answer.can anybody tell me what mistake i made?thanks!Code:#include<stdio.h> #include<stdlib.h> #include<math.h> #define PI 3.1415926 #define N 16 //the length #define W_RE (cos(-2.0*PI/N)) #define W_IM (sin(-2.0*PI/N)) void recursive_fft(double [],int,double [],double []); int main(){ double x[N] = {0.5751,0.4514,0.0439,0.0272, 0.3127,0.0129,0.3840,0.6831, 0.0928,0.0353,0.6124,0.6085, 0.0158,0.0164,0.1901,0.5869}; double y_re[N],y_im[N]; recursive_fft(x,N,y_re,y_im); /*output*/ for(int i = 0;i<N;i++){ printf("%lf",y_re[i]); if(y_im[i]) printf(" + %lfi",y_im[i]); printf("\n"); } return 0; } /*x is the input DFT，len_x is the length *y_re and y_im ===> real part and image part of the result * */ void recursive_fft(double x[],int len_x,\ double y_re[],double y_im[]){ double re_w = 1.0,im_w = 0; double x_even[len_x/2],x_odd[len_x/2]; double y1_re[len_x/2] ,y1_im[len_x/2] ; double y2_re[len_x/2] ,y2_im[len_x/2] ; int index_even = 0,index_odd = 0; for(int i=0;i<len_x/2;i++){ y1_re[i] = y1_im[i] = y2_re[i] = y2_im[i] = 0; } if(1 == len_x){ y_re[0] = x[0];y_im[0] = 0; return ; } for(int i = 0;i<len_x;i++){ if(i % 2 == 0){/*even */ x_even[index_even++] = x[i]; }else{ x_odd[index_odd++] = x[i]; } } recursive_fft(x_odd,index_odd,y1_re,y1_im); recursive_fft(x_even,index_even,y2_re,y2_im); for(int k = 0;k<len_x/2;k++){ y_re[k] = y1_re[k]*re_w - im_w*y1_im[k] + y2_re[k]; y_im[k] = y1_im[k]*re_w + y1_re[k]*im_w + y2_im[k]; y_re[k+len_x/2] = im_w*y1_im[k] - y1_re[k]*re_w + y2_re[k]; y_im[k+len_x/2] = -1*y1_im[k]*re_w - y1_re[k]*im_w + y2_im[k]; re_w = re_w*W_RE - im_w*W_IM; im_w = im_w*W_RE + re_w*W_IM; } }