【bzoj3527】[Zjoi2014]力 FFT

2016-06-01  21:36:44

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=3527

我就是一个大傻叉 微笑脸

 #include<bits/stdc++.h>
 #define inf 1000000000
 #define ll long long
 #define N 500005
 using namespace std;
 int read(){
   int x=,f=;char ch=getchar();
   while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}
   while(ch>=''&&ch<=''){x=x*+ch-'';ch=getchar();}
   return x*f;
 }
 const double Pi=acos(-1.0);
 struct CD{
   double x,y;
   CD(double a=,double b=){x=a,y=b;}
   friend CD operator + (CD n1,CD n2){return CD(n1.x+n2.x,n1.y+n2.y);}
   friend CD operator - (CD n1,CD n2){return CD(n1.x-n2.x,n1.y-n2.y);}
   friend CD operator * (CD n1,CD n2){return CD(n1.x*n2.x-n1.y*n2.y,n1.x*n2.y+n1.y*n2.x);}
 };
 CD a[N],b[N],c[N],d[N];
 int n,nn,bit;
 double q[N];
 void FFT(CD *a,int n,int type){
   for(int i=,j=;i<n;i++){
     if(j>i)swap(a[i],a[j]);
     int k=n;
     while(j&(k>>=))j&=~k;
     j|=k;
   }
   for(int i=;i<=bit;i++){
     CD w_n(cos(*type*Pi/(<<i)),sin(*type*Pi/(<<i)));
     for(int j=;j<(<<bit);j+=(<<i)){
       CD w(,);
       for(int k=j;k<j+(<<(i-));k++){
         CD tmp=a[k],tt=w*a[k+(<<(i-))];
         a[k]=tmp+tt;a[k+(<<(i-))]=tmp-tt;
         w=w*w_n;
       }
     }
   }
   if(type<)for(int i=;i<n;i++)a[i].x=a[i].x/n;
 }
 int main(){
   n=read();nn=n;
   for(int i=;i<n;i++)scanf("%lf",&q[i]),a[i]=CD(q[i],);
   for(int i=;i<n;i++)b[i].x=1.0/(double)(i*i),b[i].y=;
   n=*n-;bit=;
   while((<<bit)<n)bit++;
   n=<<bit;
   b[]=CD();
   for(int i=nn;i<n;i++)a[i]=CD(),b[i]=CD();

   FFT(a,n,);FFT(b,n,);
   for(int i=;i<n;i++)c[i]=a[i]*b[i];
   FFT(c,n,-);
   for(int i=;i<nn;i++)a[i]=CD(q[nn-i-],);
   for(int i=nn;i<n;i++)a[i]=CD();
   FFT(a,n,);
   for(int i=;i<n;i++)d[i]=a[i]*b[i];
   FFT(d,n,-);

   for(int i=;i<nn;i++)c[i].x-=d[nn-i-].x;
   for(int i=;i<nn;i++)printf("%.5lf\n",c[i].x);
   return ;
 }