HDU 4432 Sum of divisors 质因数分解

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

bool valid[100100];

void getprime(int n,int &tot,int ans[])
{
tot=0;
for (int i=2;i<=n;i++)
{
if (valid[i])
{
tot++;
ans[tot]=i;
}
for (int j=1;((j<=tot) && (i*ans[j]<=n));j++)
{
valid[i*ans[j]]=false;
if (i%ans[j]==0) break;
}
}
}

void factor(int n,int a[],int b[],int &tot,int ss[],int sstot)
{
int i,now;
tot=0;
now=n;
for (i=1;i<=sstot;i++)
if (now%ss[i]==0)
{
a[++tot]=ss[i];
b[tot]=0;
while (now%ss[i]==0)
{
++b[tot];
now/=ss[i];
}
}
if (now!=1)
{
a[++tot]=now;
b[tot]=1;
}
}

int ss[100100],sstot;
int a[100100],b[100100],tot;
int n,m;
long long sum;

void getsum(int num)
{
int x;
while (num)
{
x=num%m;
sum+=x*x;
num/=m;
}
}

void found(int x,int num)
{
int i;
int temp=num;
if (x==tot+1 && num!=0)
{
getsum(num);
return;
}
for (i=0;i<=b[x];i++)
{
found(x+1,temp);
temp*=a[x];
}
}

int ans[100100],anstop;

int main()
{
memset(valid,true,sizeof(valid));
getprime(100000,sstot,ss);
while (scanf("%d%d",&n,&m)!=EOF)
{
sum=0;
factor(n,a,b,tot,ss,sstot);
found(1,1);
anstop=0;
while (sum)
{
anstop++;
ans[anstop]=sum%m;
sum/=m;
}
for (int i=anstop;i>=1;i--)
{
if (ans[i]>=10)
{
char ch;
ch=ans[i]-10+'A';
printf("%c",ch);
}   else
{
printf("%d",ans[i]);
}
}
printf("\n");
}
return 0;
}