【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=0,f=1;char ch=getchar();
  while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
  while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
  return x*f;
}
const double Pi=acos(-1.0);
struct CD{
  double x,y;
  CD(double a=0,double b=0){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=0,j=0;i<n;i++){
    if(j>i)swap(a[i],a[j]);
    int k=n;
    while(j&(k>>=1))j&=~k;
    j|=k;
  }
  for(int i=1;i<=bit;i++){
    CD w_n(cos(2*type*Pi/(1<<i)),sin(2*type*Pi/(1<<i)));
    for(int j=0;j<(1<<bit);j+=(1<<i)){
      CD w(1,0);
      for(int k=j;k<j+(1<<(i-1));k++){
        CD tmp=a[k],tt=w*a[k+(1<<(i-1))];
        a[k]=tmp+tt;a[k+(1<<(i-1))]=tmp-tt;
        w=w*w_n;
      }
    }
  }
  if(type<0)for(int i=0;i<n;i++)a[i].x=a[i].x/n;
}
int main(){
  n=read();nn=n;
  for(int i=0;i<n;i++)scanf("%lf",&q[i]),a[i]=CD(q[i],0);
  for(int i=1;i<n;i++)b[i].x=1.0/(double)(i*i),b[i].y=0;
  n=2*n-1;bit=1;
  while((1<<bit)<n)bit++;
  n=1<<bit;
  b[0]=CD();
  for(int i=nn;i<n;i++)a[i]=CD(),b[i]=CD();
   
  FFT(a,n,1);FFT(b,n,1);
  for(int i=0;i<n;i++)c[i]=a[i]*b[i];
  FFT(c,n,-1);
  for(int i=0;i<nn;i++)a[i]=CD(q[nn-i-1],0);
  for(int i=nn;i<n;i++)a[i]=CD();
  FFT(a,n,1);
  for(int i=0;i<n;i++)d[i]=a[i]*b[i];
  FFT(d,n,-1);
   
  for(int i=0;i<nn;i++)c[i].x-=d[nn-i-1].x;
  for(int i=0;i<nn;i++)printf("%.5lf
",c[i].x);
  return 0;
}