diff options
Diffstat (limited to 'math/transforms/fft.cpp')
| -rw-r--r-- | math/transforms/fft.cpp | 23 |
1 files changed, 0 insertions, 23 deletions
diff --git a/math/transforms/fft.cpp b/math/transforms/fft.cpp deleted file mode 100644 index 2bd95b2..0000000 --- a/math/transforms/fft.cpp +++ /dev/null @@ -1,23 +0,0 @@ -using cplx = complex<double>; - -void fft(vector<cplx>& a, bool inv = false) { - int n = sz(a); - for (int i = 0, j = 1; j < n - 1; ++j) { - for (int k = n >> 1; k > (i ^= k); k >>= 1); - if (j < i) swap(a[i], a[j]); - } - static vector<cplx> ws(2, 1); - for (static int k = 2; k < n; k *= 2) { - ws.resize(n); - cplx w = polar(1.0, acos(-1.0) / k); - for (int i=k; i<2*k; i++) ws[i] = ws[i/2] * (i % 2 ? w : 1); - } - for (int s = 1; s < n; s *= 2) { - for (int j = 0; j < n; j += 2 * s) { - for (int k = 0; k < s; k++) { - cplx u = a[j + k], t = a[j + s + k]; - t *= (inv ? conj(ws[s + k]) : ws[s + k]); - a[j + k] = u + t; - a[j + s + k] = u - t; - if (inv) a[j + k] /= 2, a[j + s + k] /= 2; -}}}} |