From 009a9b1b085912eb96926597af8e5da96e8b4a9f Mon Sep 17 00:00:00 2001
From: Noobie99 <noob999noob999@gmail.com>
Date: Fri, 2 Feb 2024 19:52:58 +0100
Subject: change fft, ntt and bitwise transforms

---
 math/transforms/xorTransform.cpp | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

(limited to 'math/transforms/xorTransform.cpp')

diff --git a/math/transforms/xorTransform.cpp b/math/transforms/xorTransform.cpp
index 48e4df2..f9d1d82 100644
--- a/math/transforms/xorTransform.cpp
+++ b/math/transforms/xorTransform.cpp
@@ -1,17 +1,10 @@
-void fft(vector<ll>& a, bool inverse = 0) {
+void fft(vector<ll>& 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]);
-	}
 	for (int s = 1; s < n; s *= 2) {
-		for (int j = 0; j < n; j+= 2 * s) {
-			for (int k = 0; k < s; k++) {
-				ll u = a[j + k], t = a[j + s + k];
-				a[j + k] = u + t;
-				a[j + s + k] = u - t;
+		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) = pair(u + v, u - v);
 	}}}
-	if (inverse) {
-		for (ll i = 0; i < n; i++) {
-			a[i] /= n;
-}}}
+	if (inv) for (ll& x : a) x /= n;
+}
-- 
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