1 private static Complex[] FFT1(Complex[] f)
2 {
3 int N=f.length;
4 int power= (int) (Math.log10(N)/Math.log10(2));
5 Complex[] F=new Complex[N];
6 //按奇偶分组
7 for(int i=0;i<N;i++)
8 {
9 int p = 0;
10 for (int j = 0; j < power; j++)
11 if ((i & (1 << j)) != 0)
12 p += 1 << (power - j - 1);
13
14 F[p] = f[i];
15 }
16 //蝶形因子
17 Complex[] wc = new Complex[N/ 2];
18 for (int i = 0; i < N / 2; i++)
19 {
20 double angle = -i * Math.PI * 2 / N;
21 wc[i]=new Complex(Math.cos(angle),Math.sin(angle));
22 }
23 //蝶形运算
24 for(int L=1;L<=power;L++)//第L层数
25 {
26 int bf=1<<(power-L);//蝶形数
27 for(int n=0;n<bf;n++)//第n+1个蝶形
28 {
29 int bfsize=1<<L;//蝶形大小
30 for(int k=0;k<bfsize/2;k++)//第k+1个蝶形因子
31 {
32 Complex temp,X1,X2;;
33 int i=n*bfsize+k,
34 j=i+bfsize/2;
35 temp=wc[k*bf].Mul(F[j]);
36 X1=F[i].Add(temp);
37 X2=F[i].Sub(temp);
38 F[i]=X1;
39 F[j]=X2;
40 }
41 }
42 }
43 return F;
44 }
