1 files changed, 14 insertions, 0 deletions
diff --git a/math/transforms/fftMul.cpp b/math/transforms/fftMul.cpp
new file mode 100644
index 0000000..dc19412
--- /dev/null
+++ b/math/transforms/fftMul.cpp
@@ -0,0 +1,14 @@
+vector<cplx> mul(vector<cplx>& a, vector<cplx>& b) {
+	vector<cplx> c(a.size()), d(a.size());
+	for (int i = 0; i < b.size(); i++) {
+		c[i] = {real(a[i]), real(b[i])};
+	}
+	c = fft(c);
+	for (int i = 0; i < b.size(); i++) {
+		int j = (a.size() - i) % a.size();
+		cplx x = (c[i] + conj(c[j])) / cplx{2, 0}; //fft(a)[i];
+		cplx y = (c[i] - conj(c[j])) / cplx{0, 2}; //fft(b)[i];
+		d[i] = x * y;
+	}		
+	return fft(d, true);
+}