FFT模板

#include<bits/stdc++.h>
#define N 2621450
#define pi acos(-1) 
using namespace std;
typedef complex<double> E;
int n,m,l,r[N];
E a[N],b[N];
void fft(E *a,int f){
    for(int i=0;i<n;i++)if(i<r[i])swap(a[i],a[r[i]]);
    for(int i=1;i<n;i<<=1){
        E wn(cos(pi/i),f*sin(pi/i)); 
        for(int p=i<<1,j=0;j<n;j+=p){
            E w(1,0);
            for(int k=0;k<i;k++,w*=wn){
                E x=a[j+k],y=w*a[j+k+i];
                a[j+k]=x+y;a[j+k+i]=x-y;  
            }
        }
    }
}
inline int read(){
    int f=1,x=0;char ch;
    do{ch=getchar();if(ch=='-')f=-1;}while(ch<'0'||ch>'9');
    do{x=x*10+ch-'0';ch=getchar();}while(ch>='0'&&ch<='9');
    return f*x;
}
int main(){
    n=read();m=read();
    for(int i=0;i<=n;i++)a[i]=read();
    for(int i=0;i<=m;i++)b[i]=read();
    m+=n;for(n=1;n<=m;n<<=1)l++;
    for(int i=0;i<n;i++)r[i]=(r[i>>1]>>1)|((i&1)<<(l-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<=m;i++)printf("%d ",(int)(a[i].real()/n+0.5));
}