BZOJ3456【分治FFT】

然而会TLE.

/* I will wait for you */#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>#include <ctime>#include <algorithm>#include <iostream>#include <fstream>#include <vector>#include <queue>#include <deque>#include <set>#include <map>#include <string>#define make(a,b) make_pair(a,b)#define fi first#define se secondusing namespace std;typedef long long ll;typedef unsigned long long ull;typedef pair<int, int> pii;typedef map<int, int> mii;const int maxn = 1000010;const int maxm = 1010;const int maxs = 26;const int inf = 0x3f3f3f3f;const ll P = 479 << 21 ^ 1;const ll G = 3;const double error = 1e-9;inline ll read(){ll x = 0, f = 1; char ch = getchar();while (ch > '9' || ch < '0' )f = (ch == '-' ? -1 : 1), ch = getchar();while (ch <= '9' && ch >= '0')x = x * 10 + ch - '0', ch = getchar();return f * x;}ll n, _x[maxn], _y[maxn], rev[maxn], w[2][maxn],   f[maxn], I[maxn], nI[maxn], C[maxn];ll _pow(ll a, ll b){ll ans = 1;for (; b; a = a * a % P, b /= 2)if (b & 1) ans = ans * a % P;return ans;}void init(){n = read(), I[0] = nI[0] = 1;for (int i = 1; i <= n << 1; i++) {I[i] = I[i - 1] * i % P;nI[i] = _pow(I[i], P - 2);}for (int i = 1; i <= n << 1; i++)C[i] = _pow(2, 1ll * i * (i - 1) / 2);}void NTT(ll *a, int n, int f){for (int i = 0; i < n; i++) {rev[i] = 0;for (int j = i, k = 1; k < n; k <<= 1, j >>= 1)(rev[i] <<= 1) |= j & 1;if (rev[i] > i) swap(a[i], a[rev[i]]);}w[0][0] = w[1][0] = 1;for (int i = 1; i < n; i++) {w[0][i] = w[0][i - 1] * _pow(G, (P - 1) / n) % P;w[1][i] = _pow(w[0][i], P - 2);}for (int i = 1; i < n; i <<= 1)for (int j = 0, l = n / (i << 1); j < n; j += (i << 1))for (int k = 0, t = 0; k < i; k += 1, t += l) {ll x = a[j + k], y = w[f][t] * a[i + j + k] % P;a[j + k] = (x + y) % P, a[i + j + k] = (x - y + P) % P;}for (int i = 0; f && i < n; i++)a[i] = a[i] * _pow(n, P - 2) % P;}void solve(int l, int r){int mid = (r + l) / 2, len = 1;if (l == r) {f[mid] = C[mid] - I[mid - 1] * f[mid] % P;f[mid] = (f[mid] + P) % P; return;}while (1 << len < (r - l) << 1) len += 1;solve(l, mid);for (int i = 0; i <= 1 << len; i++)_x[i] = _y[i] = 0;for (int i = l; i <= mid; i++)_x[i - l] = nI[i - 1] * f[i] % P;for (int i = l; i <= r; i++)_y[i - l] = C[i - l] * nI[i - l] % P;NTT(_x, 1 << len, 0);NTT(_y, 1 << len, 0);for (int i = 0; i <= 1 << len; i++)_x[i] = _x[i] * _y[i] % P;NTT(_x, 1 << len, 1);for (int i = mid + 1; i <= r; i++)f[i] = (f[i] + _x[i - l]) % P;solve(mid + 1, r);}int main(){init(), solve(1, n), printf("%lld\n", f[n]);return 0;}