题解：P1304 哥德巴赫猜想

#include <bits/stdc++.h>
using namespace std;

bool isprime(int n)
{
    if (n == 1)
        return 0;
    if (n == 2)
        return 1;
    for (int i = 2; i <= sqrt(n); i++)
    {
        if (n % i == 0)
            return 0;
    }
    return 1;
}

int n;

int main()
{
    cin >> n;
    for (int i = 4; i <= n; i += 2)
    {
        for (int j = 2; j <= i; j++)
        {
            if (isprime(j))
            {
                if (isprime(i - j))
                {
                    cout << i << "=" << j << "+" << i - j << endl;
                    break;
                }
            }
        }
    }
    return 0;
}