模板：FFT

FFT模板

ｃｏｄｅ：

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
bool Finish_read;
template<class T>inline void read(T &x){Finish_read=0;x=0;int f=1;char ch=getchar();while(!isdigit(ch)){if(ch=='-')f=-1;if(ch==EOF)return;ch=getchar();}while(isdigit(ch))x=x*10+ch-'0',ch=getchar();x*=f;Finish_read=1;}
template<class T>inline void print(T x){if(x/10!=0)print(x/10);putchar(x%10+'0');}
template<class T>inline void writeln(T x){if(x<0)putchar('-');x=abs(x);print(x);putchar('\n');}
template<class T>inline void write(T x){if(x<0)putchar('-');x=abs(x);print(x);}
/*================Header Template==============*/
const int maxn=5e6+500;
const double PI=acos(-1);
int n,m;
int rev[maxn];
int lim=1,len;
/*==================Define Area================*/
struct comp {
    double r,i;
    comp() {}
    comp(double r,double i):r(r),i(i) {}
}a[maxn],b[maxn];

comp operator + (comp a,comp b) {
    return comp(a.r+b.r,a.i+b.i);
}
comp operator - (comp a,comp b) {
    return comp(a.r-b.r,a.i-b.i);
}
comp operator * (comp a,comp b) {
    return comp(a.r*b.r-a.i*b.i,a.i*b.r+a.r*b.i);
}

void GetRev() {
    for(int i=0;i<lim;i++) {
        rev[i]=(rev[i>>1]>>1)|((i&1)<<(len-1));
    }
}

void FFT(comp *a,int IDFT) {
    for(int i=0;i<lim;i++) if(i<rev[i]) swap(a[i],a[rev[i]]);
    for(int mid=1;mid<lim;mid<<=1) {
        comp w=comp(cos(PI/mid),IDFT*sin(PI/mid));
        for(int l=mid<<1,j=0;j<lim;j+=l) {
            comp wn=comp(1.0,0.0);
            for(int k=0;k<mid;k++) {
                comp x=a[k+j];
                comp y=a[k+j+mid]*wn;
                a[k+j]=x+y;
                a[k+j+mid]=x-y;
                wn=wn*w;
            }
        }
    }
}

int main() {
    read(n);read(m);
    while(lim<=n+m) lim<<=1,len++;
    GetRev();
    for(int i=0;i<=n;i++) scanf("%lf",&a[i].r);
    for(int i=0;i<=m;i++) scanf("%lf",&b[i].r);
    FFT(a,1);
    FFT(b,1);
    for(int i=0;i<lim;i++) {
        a[i]=a[i]*b[i];
    }
    FFT(a,-1);
    for(int i=0;i<=m+n;i++) {
        printf("%d ",(int)(a[i].r/lim+0.5));
    }
    return 0;
}