题解 | #查找组成一个偶数最接近的两个素数#

#include <climits>
#include <iostream>
#include <cmath> 
#include <vector>

using namespace std;

bool isPrime(int num)
{
    if (num <= 1) return false;
    if (num <= 3) return true;
    if (num % 2 == 0 || num % 3 == 0) return false;

    int i = 5;
    while (i*i <= num){
        if (num % i == 0 || num % (i+2) == 0) return false;
        i += 6;
    }
    return true;
}
int main ()
{
    int input;
    cin >> input;
    vector<int> vecPrime;

    for (int i = 2; i <= input; i++){
        if (isPrime(i)){
            vecPrime.push_back(i);
            // cout << i << endl;

        }
    }
    
    int tmp = INT_MAX;
    int n = INT_MAX,m = INT_MAX;
    for (int i = vecPrime.size() - 1; i >= 0; i--){
        for (int j = i ; j < vecPrime.size(); j++){
            if ((vecPrime[i] + vecPrime[j] == input)
                && tmp > abs(vecPrime[i] - vecPrime[j])){
                tmp = abs(vecPrime[i] - vecPrime[j]);
                
                n = vecPrime[i];
                m = vecPrime[j];
                break;
            }       
        }
    }
    if (n!=INT_MAX)
    {
        cout << n << endl;
        cout << m << endl;
    }
        
    return 0;
}