hdu 1402 A * B Problem Plus
http://acm.hdu.edu.cn/showproblem.php?pid=1402
#include
<
iostream
>
#include
<
cmath
>
using
namespace
std;
typedef
struct
vir
{
double re,im;
vir(){}
vir(double a,double b){re=a;im=b;}
vir operator +(const vir &b){ return vir(re+b.re,im+b.im);}
vir operator -(const vir &b){ return vir(re-b.re,im-b.im);}
vir operator *(const vir &b){ return vir(re*b.re-im*b.im,re*b.im+b.re*im);}
}
vir;
vir x1[
200005
],x2[
200005
];
const
double
Pi
=
acos(
-
1.0
);
void
change(vir
*
x,
int
len,
int
loglen)
{
int i,j,k,t;
for(i=0;i<len;i++)
{
t = i;
for(j=k=0;j<loglen;j++,t>>=1)
k = (k<<1)|(t&1);
if(k<i)
{
vir wt = x[k];
x[k] = x[i];
x[i] = wt;
}
}
}
void
fft(vir
*
x,
int
len,
int
loglen)
{
int i,j,t,s,e;
change(x,len,loglen);
t = 1;
for(i=0;i<loglen;i++,t<<=1)
{
s = 0;
e = s + t;
while(s<len)
{
vir a,b,wo(cos(Pi/t),sin(Pi/t)),wn(1,0);
for(j=s;j<s+t;j++)
{
a = x[j];
b = x[j+t]*wn;
x[j] = a + b;
x[j+t] = a - b;
wn =wn*wo;
}
s = e+t;
e = s+t;
}
}
}
void
dit_fft(vir
*
x,
int
len,
int
loglen)
{
int i,j,s,e,t=1<<loglen;
for(i=0;i<loglen;i++)
{
t>>=1;
s=0;
e=s+t;
while(s<len)
{
vir a,b,wn(1,0),wo(cos(Pi/t),-sin(Pi/t));
for(j=s;j<s+t;j++)
{
a = x[j]+x[j+t];
b = (x[j]-x[j+t])*wn;
x[j] = a;
x[j+t] = b;
wn = wn*wo;
}
s = e+t;
e = s+t;
}
}
change(x,len,loglen);
for(i=0;i<len;i++)
x[i].re/=len;
}
int
main()
{
char a[100005],b[100005];
int i,len1,len2,t,over,len,loglen;
while(scanf("%s%s",a,b)!=EOF)
{
len1 = strlen(a)<<1;
len2 = strlen(b)<<1;
len = 1;
loglen = 0;
while(len<len1)
{
len<<=1;
loglen++;
}
while(len<len2)
{
len<<=1;
loglen++;
}
for(i=0;a[i]!='\0';i++)
{
x1[i].re = a[i]-'0';
x1[i].im = 0;
}
for(;i<len;i++)
x1[i].re = x1[i].im = 0;
for(i=0;b[i]!='\0';i++)
{
x2[i].re = b[i]-'0';
x2[i].im = 0;
}
for(;i<len;i++)
x2[i].re = x2[i].im = 0;
fft(x1,len,loglen);
fft(x2,len,loglen);
for(i=0;i<len;i++)
x1[i] = x1[i]*x2[i];
dit_fft(x1,len,loglen);
for(i=(len1+len2)/2-2,over=loglen=0;i>=0;i--)
{
t = x1[i].re + over + 0.5;
a[loglen++] = t%10;
over = t/10;
}
while(over)
{
a[loglen++] = over%10;
over /= 10;
}
for(loglen--;loglen>=0&&!a[loglen];loglen--);
if(loglen<0)
putchar('0');
else
for(;loglen>=0;loglen--)
putchar(a[loglen]+'0');
putchar('\n');
}
return 0;
}
#include
<
iostream
>
#include
<
cmath
>
using
namespace
std;typedef
struct
vir
{ double re,im; vir(){} vir(double a,double b){re=a;im=b;} vir operator +(const vir &b){ return vir(re+b.re,im+b.im);} vir operator -(const vir &b){ return vir(re-b.re,im-b.im);} vir operator *(const vir &b){ return vir(re*b.re-im*b.im,re*b.im+b.re*im);}}
vir;vir x1[
200005
],x2[
200005
];
const
double
Pi
=
acos(
-
1.0
);
void
change(vir
*
x,
int
len,
int
loglen)
{ int i,j,k,t; for(i=0;i<len;i++) { t = i; for(j=k=0;j<loglen;j++,t>>=1) k = (k<<1)|(t&1); if(k<i) { vir wt = x[k]; x[k] = x[i]; x[i] = wt; } }}
void
fft(vir
*
x,
int
len,
int
loglen)
{ int i,j,t,s,e; change(x,len,loglen); t = 1; for(i=0;i<loglen;i++,t<<=1) { s = 0; e = s + t; while(s<len) { vir a,b,wo(cos(Pi/t),sin(Pi/t)),wn(1,0); for(j=s;j<s+t;j++) { a = x[j]; b = x[j+t]*wn; x[j] = a + b; x[j+t] = a - b; wn =wn*wo; } s = e+t; e = s+t; } }}
void
dit_fft(vir
*
x,
int
len,
int
loglen)
{ int i,j,s,e,t=1<<loglen; for(i=0;i<loglen;i++) { t>>=1; s=0; e=s+t; while(s<len) { vir a,b,wn(1,0),wo(cos(Pi/t),-sin(Pi/t)); for(j=s;j<s+t;j++) { a = x[j]+x[j+t]; b = (x[j]-x[j+t])*wn; x[j] = a; x[j+t] = b; wn = wn*wo; } s = e+t; e = s+t; } } change(x,len,loglen); for(i=0;i<len;i++) x[i].re/=len;}
int
main()
{ char a[100005],b[100005]; int i,len1,len2,t,over,len,loglen; while(scanf("%s%s",a,b)!=EOF) { len1 = strlen(a)<<1; len2 = strlen(b)<<1; len = 1; loglen = 0; while(len<len1) { len<<=1; loglen++; } while(len<len2) { len<<=1; loglen++; } for(i=0;a[i]!='\0';i++) { x1[i].re = a[i]-'0'; x1[i].im = 0; } for(;i<len;i++) x1[i].re = x1[i].im = 0; for(i=0;b[i]!='\0';i++) { x2[i].re = b[i]-'0'; x2[i].im = 0; } for(;i<len;i++) x2[i].re = x2[i].im = 0; fft(x1,len,loglen); fft(x2,len,loglen); for(i=0;i<len;i++) x1[i] = x1[i]*x2[i]; dit_fft(x1,len,loglen); for(i=(len1+len2)/2-2,over=loglen=0;i>=0;i--) { t = x1[i].re + over + 0.5; a[loglen++] = t%10; over = t/10; } while(over) { a[loglen++] = over%10; over /= 10; } for(loglen--;loglen>=0&&!a[loglen];loglen--); if(loglen<0) putchar('0'); else for(;loglen>=0;loglen--) putchar(a[loglen]+'0'); putchar('\n'); } return 0;}