Module
#define L(x) (1 << (x)) const double PI = acos(-1.0); const int N = 17, Maxn = L(N + 1); double ax[Maxn], ay[Maxn], bx[Maxn], by[Maxn] struct FFT { private : int revv(int x, int bits) { int ret = 0; for (int i = 0; i < bits; i++) { ret <<= 1; ret |= x & 1; x >>= 1; } return ret; } void fft(double * a, double * b, int n, bool rev) { int bits = 0; while (1 << bits < n) ++bits; for (int i = 0; i < n; i++) { int j = revv(i, bits); if (i < j) { double t = a[i]; a[i] = a[j]; a[j] = t; t = b[i]; b[i] = b[j]; b[j] = t; } } for (int len = 2; len <= n; len <<= 1) { int half = len >> 1; double wmx = cos(2 * PI / len); double wmy = sin(2 * PI / len); if (rev) wmy = -wmy; for (int i = 0; i < n; i += len) { double wx = 1; double wy = 0; for (int j = 0; j < half; j++) { double cx = a[i + j]; double cy = b[i + j]; double dx = a[i + j + half]; double dy = b[i + j + half]; double ex = dx * wx - dy * wy; double ey = dx * wy + dy * wx; a[i + j] = cx + ex; b[i + j] = cy + ey; a[i + j + half] = cx - ex; b[i + j + half] = cy - ey; double wnx = wx * wmx - wy * wmy; double wny = wx * wmy + wy * wmx; wx = wnx; wy = wny; } } } if (rev) { for (int i = 0; i < n; i++) { a[i] /= n; b[i] /= n; } } } public: int solve(int a[],int na,int b[],int nb,long long ans[]) { int len = max(na, nb), ln; for(ln=0; L(ln)<len; ++ln); len=L(++ln); for (int i = 0; i < len ; ++i) { if (i >= na) ax[i] = 0, bx[i] =0; else ax[i] = a[i], bx[i] = 0; } fft(ax, ay, len, 0); for (int i = 0; i < len; ++i) { if (i >= nb) bx[i] = 0, by[i] = 0; else bx[i] = b[i], by[i] = 0; } fft(bx, by, len, 0); for (int i = 0; i < len; ++i) { double cx = ax[i] * bx[i] - ay[i] * by[i]; double cy = ax[i] * by[i] + ay[i] * bx[i]; ax[i] = cx, ay[i] = cy; } fft(ax, ay, len, 1); for (int i = 0; i < len; ++i) ans[i] = ax[i] + 0.01; return len; } int solve(int a[], int na, long long ans[]) { int len = na, ln; for(ln = 0; L(ln) < na; ++ln); len=L(++ln); for(int i = 0;i < len; ++i) { if (i >= na) ax[i] = 0, ay[i] = 0; else ax[i] = a[i], ay[i] = 0; } fft(ax, ay, len, 0); for(int i=0;i<len;++i) { double cx = ax[i] * ax[i] - ay[i] * ay[i]; double cy = 2 * ax[i] * ay[i]; ax[i] = cx, ay[i] = cy; } fft(ax, ay, len, 1); for(int i=0;i<len;++i) ans[i] = ax[i] + 0.5; return len; } };