HDU 3589 Jacobi symbol

彻底对数学绝望了

#include <cstdio>
#include <cmath>
int flag[1005],p[500],a;
int d[100];
int init(int s)
{
    int len=0,tmp,h=sqrt(s+0.5);
    for(int i=0;p[i]<=h;i++)
    if(s%p[i]==0)
    {
        if(a%p[i]==0)return -1;
        while(s%p[i]==0)
        {
            d[len++]=p[i];
            s/=p[i];
        }
        if(s==1)return len;
    }
    if(s>1)
    {
        if(a%s==0)return -1;
        d[len++]=s;
    }
    return len;
}
int getans(int x,int s)
{
    int tmp=s/2;
    __int64 ans=1,b=x;
    while(tmp>0)
    {
        if(tmp&1)ans=ans*b%s;
        b=b*b%s;
        tmp/=2;
    }
    if(ans!=1)return -1;
    return 1;
}
int main()
{
    int i,j,k=0,n;
    for(i=2;i<1000;i++)
    {
        if(!flag[i])
        {
            p[k++]=i;
            for(j=i*i;j<1000;j+=i)
                flag[j]=1;
        }
    }
    while(scanf("%d%d",&a,&n)!=-1)
    {
        int len=init(n);
        if(len==-1)
        {
            printf("0\n");
            continue;
        }
        int ans=1;
        for(i=0;i<len;i++)
            ans*=getans(a,d[i]);
        printf("%d\n",ans);
    }
    return 0;
}