63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
template <ll M>
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void ntt(vector<MLL<M>>& y, bool idft) {
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using mll = MLL<M>;
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int n = y.size();
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vector<int> rev(n);
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for (int i = 0; i < n; ++i) {
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rev[i] = rev[i >> 1] >> 1;
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if (i & 1) {
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rev[i] |= n >> 1;
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}
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}
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for (int i = 0; i < n; ++i) {
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if (i < rev[i]) {
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swap(y[i], y[rev[i]]);
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}
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}
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vector<mll> roots = { 0, 1 };
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if (roots.size() < n) {
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int k = lsp(roots.size());
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roots.resize(n);
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for (; (1 << k) < n; ++k) {
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mll e = qpow<mll>(31, 1 << lsp(M - 1) - k - 1);
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for (int i = 1 << k - 1; i < (1 << k); ++i) {
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roots[2 * i] = roots[i];
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roots[2 * i + 1] = roots[i] * e;
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}
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}
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}
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for (int h = 2; h <= n; h <<= 1) {
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for (int j = 0; j < n; j += h) {
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for (int k = j; k < j + h / 2; ++k) {
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mll u = y[k], t = roots[k - j + h / 2] * y[k + h / 2];
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y[k] = u + t;
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y[k + h / 2] = u - t;
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}
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}
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}
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if (idft) {
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reverse(y.begin() + 1, y.end());
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for (int i = 0; i < n; ++i) {
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y[i] /= n;
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}
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}
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}
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template <ll M>
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vector<MLL<M>> multiply(const vector<MLL<M>>& a, const vector<MLL<M>>& b) {
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using mll = MLL<M>;
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vector<mll> A(a.begin(), a.end()), B(b.begin(), b.end());
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int n = 1;
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while (n < a.size() + b.size()) n <<= 1;
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A.resize(n), B.resize(n);
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ntt<M>(A, false), ntt<M>(B, false);
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for (int i = 0; i < n; ++i) {
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A[i] *= B[i];
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}
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ntt<M>(A, true);
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A.resize(a.size() + b.size() - 1);
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return A;
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}
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