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;

}