dft(多項式相乘模板)

/*Author : lifehappy */ #pragma GCC optimize(2) #pragma GCC optimize(3) #include <bits/stdc++.h>using namespace std;const double pi = acos(-1.0);const int N = 3e6 + 10;struct Complex {double r, i;Complex(double _r = 0, double _i = 0) : r(_r), i(_i) {} }a[N], b[N];Complex operator + (const Complex & a, const Complex & b) {return Complex(a.r + b.r, a.i + b.i); }Complex operator - (const Complex & a, const Complex & b) {return Complex(a.r - b.r, a.i - b.i); }Complex operator * (const Complex & a, const Complex & b) {return Complex(a.r * b.r - a.i * b.i, a.r * b.i + a.i * b.r); }int n, m;void dft(Complex *f, int lim, int rev) {if(!lim) return ;Complex a1[lim], a2[lim];for(int i = 0; i < lim; i++) {a1[i] = f[i << 1], a2[i] = f[i << 1 | 1];}dft(a1, lim >> 1, rev);dft(a2, lim >> 1, rev);Complex wn = Complex(cos(pi / lim), rev * sin(pi / lim)), w = Complex(1, 0);for(int i = 0; i < lim; i++, w = w * wn) {f[i] = a1[i] + w * a2[i];f[i + lim] = a1[i] - w * a2[i];} }int main() {// freopen("in.txt", "r", stdin);// freopen("out.txt", "w", stdout);// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);scanf("%d %d", &n, &m);for(int i = 0; i <= n; i++) {scanf("%lf", &a[i].r);}for(int i = 0; i <= m; i++) {scanf("%lf", &b[i].r);}int lim = 1;while(lim <= n + m) lim <<= 1;dft(a, lim >> 1, 1);//dftdft(b, lim >> 1, 1);//dftfor(int i = 0; i < lim; i++) {a[i] = a[i] * b[i];}dft(a, lim >> 1, -1);//idftfor(int i = 0; i <= n + m; i++) {printf("%d%c", int(a[i].r / lim + 0.5), i == n + m ? '\n' : ' ');}return 0; }

fft(大數乘法模板)

/*Author : lifehappy */ #include <bits/stdc++.h>using namespace std;const double pi = acos(-1.0);const int N = 5e6 + 10;struct Complex {double r, i;Complex(double _r = 0, double _i = 0) : r(_r), i(_i) {}}a[N], b[N];Complex operator + (const Complex & a, const Complex & b) {return Complex(a.r + b.r, a.i + b.i); }Complex operator - (const Complex & a, const Complex & b) {return Complex(a.r - b.r, a.i - b.i); }Complex operator * (const Complex & a, const Complex & b) {return Complex(a.r * b.r - a.i * b.i, a.r * b.i + a.i * b.r); }char str1[N], str2[N];int r[N], ans[N];void fft(Complex * f, int lim, int rev) {for(int i = 0; i < lim; i++) {if(r[i] < i) {swap(f[i], f[r[i]]);}}for(int i = 1; i < lim; i <<= 1) {Complex wn = Complex(cos(pi / i), rev * sin(pi / i));for(int p = i << 1, j = 0; j < lim; j += p) {Complex w = Complex(1, 0);for(int k = 0; k < i; k++, w = w * wn) {Complex x = f[j + k], y = w * f[i + j + k];f[j + k] = x + y, f[i + j + k] = x - y;}}}if(rev == -1) {for(int i = 0; i < lim; i++) {f[i].r /= lim;}} }int main() {// freopen("in.txt", "r", stdin);// freopen("out.txt", "w", stdout);// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);int n, m, lim;while(scanf("%s %s", str1, str2) != EOF) {n = strlen(str1), m = strlen(str2);for(int i = 0; i < n; i++) {a[i] = Complex(str1[n - i - 1] - '0', 0);}for(int i = 0; i < m; i++) {b[i] = Complex(str2[m - i - 1] - '0', 0);}lim = 1;while(lim < (n << 1) || lim < (m << 1)) lim <<= 1;for(int i = 0; i < lim; ++i) {r[i] = (i & 1) * (lim >> 1) + (r[i >> 1] >> 1);}for(int i = n; i < lim; i++) {a[i] = Complex(0, 0);}for(int i = m; i < lim; i++) {b[i] = Complex(0, 0);}fft(a, lim, 1);fft(b, lim, 1);for(int i = 0; i < lim; i++) {a[i] = a[i] * b[i];}fft(a, lim, -1);for(int i = 0; i < lim; i++){ans[i] = int(a[i].r + 0.5);}for(int i = 0; i < lim; i++){ans[i + 1] += ans[i] / 10;ans[i] %= 10;}lim = n + m - 1;while(ans[lim] <= 0 && lim > 0) lim--;for(int i = lim; i >= 0; i--){printf("%d", ans[i]);}printf("\n");}return 0; } 創作挑戰賽新人創作獎勵來咯，堅持創作打卡瓜分現金大獎

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