## FFT在一个单一的C文件的问题？内容来源于 Stack Overflow，并遵循CC BY-SA 3.0许可协议进行翻译与使用

• 回答 (2)
• 关注 (0)
• 查看 (28)

```#include <iostream>
#include <complex>
#define MAX 200

using namespace std;

#define M_PI 3.1415926535897932384

int log2(int N)    /*function to calculate the log2(.) of int numbers*/
{
int k = N, i = 0;
while(k) {
k >>= 1;
i++;
}
return i - 1;
}

int check(int n)    //checking if the number of element is a power of 2
{
return n > 0 && (n & (n - 1)) == 0;
}

int reverse(int N, int n)    //calculating revers number
{
int j, p = 0;
for(j = 1; j <= log2(N); j++) {
if(n & (1 << (log2(N) - j)))
p |= 1 << (j - 1);
}
return p;
}

void ordina(complex<double>* f1, int N) //using the reverse order in the array
{
complex<double> f2[MAX];
for(int i = 0; i < N; i++)
f2[i] = f1[reverse(N, i)];
for(int j = 0; j < N; j++)
f1[j] = f2[j];
}

void transform(complex<double>* f, int N) //
{
ordina(f, N);    //first: reverse order
complex<double> *W;
W = (complex<double> *)malloc(N / 2 * sizeof(complex<double>));
W[1] = polar(1., -2. * M_PI / N);
W[0] = 1;
for(int i = 2; i < N / 2; i++)
W[i] = pow(W[1], i);
int n = 1;
int a = N / 2;
for(int j = 0; j < log2(N); j++) {
for(int i = 0; i < N; i++) {
if(!(i & n)) {
complex<double> temp = f[i];
complex<double> Temp = W[(i * a) % (n * a)] * f[i + n];
f[i] = temp + Temp;
f[i + n] = temp - Temp;
}
}
n *= 2;
a = a / 2;
}
}

void FFT(complex<double>* f, int N, double d)
{
transform(f, N);
for(int i = 0; i < N; i++)
f[i] *= d; //multiplying by step
}

int main()
{
int n;
do {
cout << "specify array dimension (MUST be power of 2)" << endl;
cin >> n;
} while(!check(n));
double d;
cout << "specify sampling step" << endl; //just write 1 in order to have the same results of matlab fft(.)
cin >> d;
complex<double> vec[MAX];
cout << "specify the array" << endl;
for(int i = 0; i < n; i++) {
cout << "specify element number: " << i << endl;
cin >> vec[i];
}
FFT(vec, n, d);
cout << "...printing the FFT of the array specified" << endl;
for(int j = 0; j < n; j++)
cout << vec[j] << endl;
return 0;
}```

Eli Qiao

### 欠费资源销毁怎么解决？

renzha.net · 站长 (已认证)

www.renzha.net

### React项目的try_files机制，在COS上怎么配置？

galenye

COS的静态网站可以设置默认索引，你这里应该是想实现react-router spa场景下刷新浏览器时，不希望报404的场景吧 可以在COS静态网站这设置一个错误文档的默认索引来实现类似try_files的功能 image.png ... 展开详请