BZOJ 1041 圆上的整点

感谢http://hzwer.com/1457.html

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;
long long r,ans=0;
long long gcd(long long a,long long b)
{
    if (b==0) return a;
    else return gcd(b,a%b);
}
bool check(long long a,long long r)
{
    long long b=sqrt(r-a*a);
    if ((a*a+b*b==r) && (gcd(a,b)==1) && (b!=0) && (a<b))
        return true;
    return false;
}
int main()
{
    scanf("%lld",&r);
    for (long long d=1;d<=sqrt(2*r);d++)
    {
        if (2*r%d==0)
        {
            for (long long i=1;i<=sqrt(2*r/d);i++)
                if (check(i,2*r/d)) ans++;
            if (d!=(2*r)/d)
            {
                for (long long i=1;i<=sqrt(d);i++)
                    if (check(i,d)) ans++;
            }
        }
    }
    printf("%lld\n",ans*4+4);
    return 0;
}