Problem 46 Goldbach's other conjecture （暴力...）

Goldbach's other conjecture

Problem 46

It was proposed by Christian Goldbach that every odd composite number can be written as the sum of a prime and twice a square.

9 = 7 + 2×1²
15 = 7 + 2×2²
21 = 3 + 2×3²
25 = 7 + 2×3²
27 = 19 + 2×2²
33 = 31 + 2×1²

It turns out that the conjecture was false.

What is the smallest odd composite that cannot be written as the sum of a prime and twice a square?

代码：

#include<bits/stdc++.h>
using namespace std;
int isprim(int n)  //素数判断
{
    for(int i=2; i*i<=n; i++)
    {
        if(n%i==0) return 0;
    }
    return 1;
}

int judge(long long n)
{
    int i=1;
    long long t;
    while((t=(n-2*(i*i)))>0)
    {
        if(isprim(t)) return 1;
        i++;
    }
    return 0;
}

int main()
{
    for(long long i=1001; i<100000000; i+=2)
    {
        if(!isprim(i) && !judge(i))  //不是素数  
        {
            printf("%lld\n",i);
            break;
        }
    }
    return 0;
}