【模板】快速傅里叶变换

uoj34

#include<bits/stdc++.h>
#define db double
using namespace std;
const int N=400010;
const db PI=acos(-1);
int n,m,tot,maxp,rev[N];
struct Com{
    db real,image;
    Com operator+(const Com& k)const{return (Com){real+k.real,image+k.image};};
    Com operator-(const Com& k)const{return (Com){real-k.real,image-k.image};};
    Com operator*(const Com& k)const{return (Com){real*k.real-image*k.image,real*k.image+image*k.real};};
    Com operator/(const int k)const{return (Com){real/k,image/k};};
}a[N],b[N];
void fft(Com* a,int b){
    for(int i=0;i<n;i++) if(rev[i]>i) swap(a[i],a[rev[i]]);
    for(int len=2;len<=n;len<<=1){
        Com wn=(Com){cos(2.0*PI/len),sin(2.0*PI/len)*b};
        for(int i=0;i<n;i+=len){
            Com w=(Com){1,0};
            for(int j=0;j<(len>>1);j++,w=w*wn){
                Com x=a[i+j],y=a[i+j+(len>>1)]*w;
                a[i+j]=x+y,a[i+j+(len>>1)]=x-y;
            }
        }
    }
    if(b==-1) for(int i=0;i<n;i++) a[i]=a[i]/n;
    return;
}
int main(){
    scanf("%d%d",&n,&m);
    for(int i=0;i<=n;i++) scanf("%lf",&a[i].real);
    for(int i=0;i<=m;i++) scanf("%lf",&b[i].real);
    tot=n+m,n=1;
    while(n<=tot) n<<=1,maxp++;
    for(int i=1;i<n;i++) rev[i]=(rev[i>>1]>>1)|((i&1)<<(maxp-1));
    fft(a,1);fft(b,1);
    for(int i=0;i<n;i++) a[i]=a[i]*b[i];
    fft(a,-1);
    for(int i=0;i<=tot;i++) printf("%d ",int(a[i].real+0.1));
    return 0;
}