hdu 5730(分治FFT)

来源：互联网发布：小米手环数据修改攻略编辑：程序博客网时间：2024/04/27 07:32
dp[i] = sigma(a[j] * dp[i-j]) (j < i);
看这里
#include <bits/stdc++.h>#pragma comment(linker, "/STACK:102400000,102400000")using namespace std;#define LL long long#define pii pair<int,int>#define MP make_pair#define ls i << 1#define rs ls | 1#define md (ll + rr >> 1)#define lson ll, md, ls#define rson md + 1, rr, rs#define Pi acos(-1.0)#define mod 1000000007#define eps 1e-12#define inf 0x3f3f3f3f#define N 200010#define M 1200020struct Complex{    double r, i;    Complex(double r = 0, double i = 0) : r(r), i(i) {}    Complex operator + (const Complex &b) const {        return Complex(r + b.r, i + b.i);    }    Complex operator - (const Complex &b) const {        return Complex(r - b.r, i - b.i);    }    Complex operator * (const Complex &b) const {        return Complex(r * b.r - i * b.i, r * b.i + b.r * i);    }};void change(Complex *y, int len){    for(int i = 1, j = len >> 1; i < len - 1; ++i){        if(i < j) swap(y[i], y[j]);        int k = len >> 1;        while(j >= k)            j -= k, k >>= 1;        if(j < k) j += k;    }}void FFT(Complex *y, int len, int on){    change(y, len);    for(int h = 2; h <= len; h <<= 1){        Complex wn = Complex(cos(-on*2*Pi/h), sin(-on*2*Pi/h));        for(int j = 0; j < len; j += h){            Complex w = Complex(1, 0);            for(int k = j; k < j + h / 2; ++k){                Complex u = y[k];                Complex t = w * y[k+h/2];                y[k] = u + t;                y[k+h/2] = u - t;                w = w * wn;            }        }    }    if(on == -1){        for(int i = 0; i < len; ++i)            y[i].r /= len;    }}int dp[N], a[N];Complex x[N<<2], y[N<<2];void solve(int L, int R){    if(L == R) return ;    int mid = (L + R) >> 1;    solve(L, mid);    int len = 1, len1 = R - L + 1;    while(len <= len1) len <<= 1;    for(int i = 0; i < len1; ++i) x[i] = Complex(a[i], 0);    for(int i = len1; i <= len; ++i) x[i] = Complex(0, 0);    for(int i = L; i <= mid; ++i)        y[i-L] = Complex(dp[i], 0);    for(int i = mid - L + 1; i <= len; ++i) y[i] = Complex(0, 0);    FFT(x, len, 1);    FFT(y, len, 1);    for(int i = 0; i < len; ++i) x[i] = x[i] * y[i];    FFT(x, len, -1);    for(int i = mid + 1; i <= R; ++i){        dp[i] += x[i-L].r + 0.5;        dp[i] %= 313;    }    solve(mid + 1, R);}int main(){    int n;    while(scanf("%d", &n) != EOF && n){        for(int i = 1; i <= n; ++i)            scanf("%d", &a[i]), a[i] %= 313;        for(int i = 1; i <= n; ++i) dp[i] = 0;        dp[0] = 1;        solve(0, n);        printf("%d\n", dp[n]);    }    return 0;}
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