FFT

mamaya我终于会FFT啦....

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#include<iostream>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<complex>
using namespace std;
#define maxn 1001000
#define llg long long 
#define Pi acos(-1.0)
#define yyj(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
typedef complex<double> XU;

struct FFT
{
    llg rev[maxn],L,n,m,c[maxn];
    
    void fft(XU *z,llg f)
    {
        for (llg i=0;i<n;i++) if (i<rev[i]) swap(z[i],z[rev[i]]);
        for (llg i=1;i<n;i*=2)
        {
            XU wn(cos(Pi/i),sin(Pi/i));
            for (llg p=i*2,j=0;j<n;j+=p)
            {
                XU w(1,0);
                for (llg k=0;k<i;k++,w*=wn)
                {
                    XU x=z[j+k],y=w*z[j+k+i];
                    z[j+k]=x+y,z[j+k+i]=x-y;
                }
            }
        }
        if (f==-1) reverse(z+1,z+n);
    }

    XU a[maxn],b[maxn];

    void work()
    {
        m+=n;
        for (n=1;n<=m;n*=2) L++;
        for (llg i=0;i<n;i++) rev[i]=(rev[i/2]/2)|((i&1)<<(L-1));
        fft(a,1); fft(b,1);
        for (llg i=0;i<n;i++) a[i]=a[i]*b[i];
        fft(a,-1);
        for (llg i=0;i<=m;i++) c[i]=(llg)(a[i].real()/n+0.5);
    }

}fft;

llg read() {llg x; scanf("%lld",&x); return x;}

int main()
{
    yyj("fft");
    cin>>fft.n>>fft.m;
    for (llg i=0;i<=fft.n;i++) fft.a[i]=read();
    for (llg i=0;i<=fft.m;i++) fft.b[i]=read();
    fft.work();
    for (llg i=0;i<=fft.m;i++) printf("%lld ",fft.c[i]);
    return 0;
}