change fft, ntt and bitwise transforms

1 files changed, 12 insertions, 0 deletions

diff --git a/math/transforms/bitwiseTransforms.cpp b/math/transforms/bitwiseTransforms.cpp
new file mode 100644
index 0000000..7d1f80d
--- /dev/null
+++ b/math/transforms/bitwiseTransforms.cpp
@@ -0,0 +1,12 @@
+void fft(vector<ll>& a, bool inv = false) {
+	int n = sz(a);
+	for (int s = 1; s < n; s *= 2) {
+		for (int i = 0; i < n; i += 2 * s) {
+			for (int j = i; j < i + s; j++) {
+				ll& u = a[j], &v = a[j + s];
+				tie(u, v) = inv ? pair(v - u, u) : pair(v, u + v); // AND
+				//tie(u, v) = inv ? pair(v, u - v) : pair(u + v, u); //OR
+				//tie(u, v) = pair(u + v, u - v); // XOR
+	}}}
+	//if (inv) for (ll& x : a) x /= n; // XOR (careful with MOD)
+}