updated tcr

1 files changed, 8 insertions, 0 deletions

diff --git a/math/transforms/fftPerm.cpp b/math/transforms/fftPerm.cpp
new file mode 100644
index 0000000..2b6fb10
--- /dev/null
+++ b/math/transforms/fftPerm.cpp
@@ -0,0 +1,8 @@
+int perm[MAXN]; //perm[i] = j in Zeile 10
+void genPerm(int n){
+	ull mask = ~0ull << (__lg(n) - 1);
+	for (int i = 0, j = 0; i < n; i++) {
+		perm[i] = j; //if (i < j) swap(a[i], a[j]);
+		ull y = mask >> __builtin_ctz(~i);
+		j ^= y & (n - 1);
+}}