版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/qq_25576697/article/details/82026186
hdu1402
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<string.h>
using namespace std;
const int maxn = 100010;
const double PI = acos(-1.0);
//复数结构体
struct complex
{
double r,i;
complex(double _r = 0.0,double _i = 0.0)
{
r = _r; i = _i;
}
complex operator +(const complex &b)
{
return complex(r+b.r,i+b.i);
}
complex operator -(const complex &b)
{
return complex(r-b.r,i-b.i);
}
complex operator *(const complex &b)
{
return complex(r*b.r-i*b.i,r*b.i+i*b.r);
}
};
/*
* 进行FFT和IFFT前的反转变换。
* 位置i和 (i二进制反转后位置)互换
* len必须去2的幂
*/
void change(complex y[],int len)
{
int i,j,k;
for(i = 1, j = len/2;i < len-1; i++)
{
if(i < j)swap(y[i],y[j]);
//交换互为小标反转的元素,i<j保证交换一次
//i做正常的+1,j左反转类型的+1,始终保持i和j是反转的
k = len/2;
while( j >= k)
{
j -= k;
k /= 2;
}
if(j < k) j += k;
}
}
/*
* 做FFT
* len必须为2^k形式,
* on==1时是DFT,on==-1时是IDFT
*/
void fft(complex y[],int len,int on)
{
change(y,len);
for(int h = 2; h <= len; h <<= 1)
{
complex wn(cos(-on*2*PI/h),sin(-on*2*PI/h));
for(int j = 0;j < len;j+=h)
{
complex w(1,0);
for(int k = j;k < j+h/2;k++)
{
complex u = y[k];
complex t = w*y[k+h/2];
y[k] = u+t;
y[k+h/2] = u-t;
w = w*wn;
}
}
}
if(on == -1)
for(int i = 0;i < len;i++)
y[i].r /= len;
}
complex a[maxn*2],b[maxn*2];
int ans[maxn*2];
int main()
{
char s1[maxn],s2[maxn];
while(~scanf("%s%s",s1,s2))
{
int len1 = strlen(s1);
int len2 = strlen(s2);
int len = 1;
while(len<len1*2||len<len2*2)len<<=1;
for(int i = 0;i<len1;i++)
a[i] = complex(s1[len1-i-1]-'0',0);
for(int i = len1;i<len;i++)a[i] = complex(0,0);
for(int i = 0;i<len2;i++)
b[i] = complex(s2[len2-i-1]-'0',0);
for(int i = len2;i<len;i++)b[i] = complex(0,0);
fft(a,len,1);
fft(b,len,1);
for(int i = 0;i<len;i++)a[i] = a[i]*b[i];
fft(a,len,-1);
for(int i = 0;i<len;i++)
{
ans[i] = (int)(a[i].r+0.5);
}
for(int i = 0;i<len;i++)
{
ans[i+1] += ans[i]/10;
ans[i] %= 10;
}
int p;
for(int i = len-1;i>0;i--)
{
if(ans[i])
{
p = i;
break;
}
}
for(int i = p;i>=0;i--)printf("%d",ans[i]);
printf("\n");
}
}
hdu4609
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<string.h>
using namespace std;
typedef long long ll;
const int maxn = 400010;
const double PI = acos(-1.0);
//复数结构体
struct complex
{
double r,i;
complex(double _r = 0.0,double _i = 0.0)
{
r = _r; i = _i;
}
complex operator +(const complex &b)
{
return complex(r+b.r,i+b.i);
}
complex operator -(const complex &b)
{
return complex(r-b.r,i-b.i);
}
complex operator *(const complex &b)
{
return complex(r*b.r-i*b.i,r*b.i+i*b.r);
}
};
/*
* 进行FFT和IFFT前的反转变换。
* 位置i和 (i二进制反转后位置)互换
* len必须去2的幂
*/
void change(complex y[],int len)
{
int i,j,k;
for(i = 1, j = len/2;i < len-1; i++)
{
if(i < j)swap(y[i],y[j]);
//交换互为小标反转的元素,i<j保证交换一次
//i做正常的+1,j左反转类型的+1,始终保持i和j是反转的
k = len/2;
while( j >= k)
{
j -= k;
k /= 2;
}
if(j < k) j += k;
}
}
/*
* 做FFT
* len必须为2^k形式,
* on==1时是DFT,on==-1时是IDFT
*/
void fft(complex y[],int len,int on)
{
change(y,len);
for(int h = 2; h <= len; h <<= 1)
{
complex wn(cos(-on*2*PI/h),sin(-on*2*PI/h));
for(int j = 0;j < len;j+=h)
{
complex w(1,0);
for(int k = j;k < j+h/2;k++)
{
complex u = y[k];
complex t = w*y[k+h/2];
y[k] = u+t;
y[k+h/2] = u-t;
w = w*wn;
}
}
}
if(on == -1)
for(int i = 0;i < len;i++)
y[i].r /= len;
}
complex a[maxn];
int x[maxn/2];
ll sum[maxn];
int main()
{
int t;
scanf("%d",&t);
while(t--)
{
int n;
scanf("%d",&n);
memset(a,0,sizeof(a));
for(int i = 0;i<n;i++)
{
scanf("%d",&x[i]);
a[x[i]].r++;
}
sort(x,x+n);
int maxl = x[n-1]+1;
int len = 1;
while(len<maxl*2)len<<=1;
fft(a,len,1);
for(int i = 0;i<len;i++)a[i] = a[i]*a[i];
fft(a,len,-1);
for(int i = 0;i<len;i++)sum[i] = (ll)(a[i].r+0.5);
for(int i = 0;i<n;i++)sum[x[i]+x[i]]--;
for(int i = 0;i<len;i++)sum[i] /= 2;
for(int i = 1;i<len;i++)sum[i] = sum[i-1]+sum[i];
ll tot = (ll)n*(n-1)*(n-2)/6;
ll cnt = 0;
for(int i = 2;i<n;i++)
{
cnt += sum[len-1]-sum[x[i]];
cnt -= (ll)(n-1-i);
cnt -= (ll)i;
cnt -= (ll)i*(n-1-i);
cnt -= (ll)(n-i-1)*(n-i-2)/2;
}
printf("%.7lf\n",(double)cnt/tot);
}
}
bzoj3527
#include<iostream>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<string.h>
using namespace std;
typedef long long ll;
const int maxn = 400100;
const double PI = acos(-1.0);
//复数结构体
struct complex
{
double r,i;
complex(double _r = 0.0,double _i = 0.0)
{
r = _r; i = _i;
}
complex operator +(const complex &b)
{
return complex(r+b.r,i+b.i);
}
complex operator -(const complex &b)
{
return complex(r-b.r,i-b.i);
}
complex operator *(const complex &b)
{
return complex(r*b.r-i*b.i,r*b.i+i*b.r);
}
};
/*
* 进行FFT和IFFT前的反转变换。
* 位置i和 (i二进制反转后位置)互换
* len必须去2的幂
*/
void change(complex y[],int len)
{
int i,j,k;
for(i = 1, j = len/2;i < len-1; i++)
{
if(i < j)swap(y[i],y[j]);
//交换互为小标反转的元素,i<j保证交换一次
//i做正常的+1,j左反转类型的+1,始终保持i和j是反转的
k = len/2;
while( j >= k)
{
j -= k;
k /= 2;
}
if(j < k) j += k;
}
}
/*
* 做FFT
* len必须为2^k形式,
* on==1时是DFT,on==-1时是IDFT
*/
void fft(complex y[],int len,int on)
{
change(y,len);
for(int h = 2; h <= len; h <<= 1)
{
complex wn(cos(-on*2*PI/h),sin(-on*2*PI/h));
for(int j = 0;j < len;j+=h)
{
complex w(1,0);
for(int k = j;k < j+h/2;k++)
{
complex u = y[k];
complex t = w*y[k+h/2];
y[k] = u+t;
y[k+h/2] = u-t;
w = w*wn;
}
}
}
if(on == -1)
for(int i = 0;i < len;i++)
y[i].r /= len;
}
complex g[maxn],f[maxn],h[maxn];
double q[maxn];
int main()
{
memset(f,0,sizeof(f));
memset(h,0,sizeof(h));
memset(g,0,sizeof(g));
int n;
scanf("%d",&n);
for(int i = 0;i<n;i++)
{
scanf("%lf",&f[i].r);
h[n-1-i].r = f[i].r;
q[i] = f[i].r;
}
g[0] = 0;
for(int i = 1;i<n;i++)
{
g[i].r = 1.0/(double)i/(double)i;
}
int len = 1;
while(len<n*2)len<<=1;
fft(g,len,1);
fft(f,len,1);
fft(h,len,1);
for(int i = 0;i<len;i++)
{
f[i] = f[i]*g[i];
h[i] = h[i]*g[i];
}
fft(f,len,-1);
fft(h,len,-1);
for(int i = 0;i<n;i++)
{
printf("%.8lf\n",(f[i].r - h[n-1-i].r));
}
}