28、＜简单＞歌德巴赫猜想

#include <iostream> using namespace std; // 判断一个数是否是素数 bool isPrime(int num) { if (num < 2) return false; for (int i = 2; i * i <= num; i++) { if (num % i == 0) return false; } return true; } int main() { cout << "输入要求：输入整数n，范围 4 ≤ n ≤ 200" << endl; cout << "功能：列出所有≤n的偶数拆分为两个素数之和的全部方案" << endl; cout << "请输入整数n："; int n; cin >> n; // 遍历所有大于等于4、小于等于n的偶数 for (int even = 4; even <= n; even += 2) { // 遍历第一个素数，保证 a ≤ b 避免重复 for (int a = 2; a <= even / 2; a++) { int b = even - a; if (isPrime(a) && isPrime(b)) { cout << even << "=" << a << "+" << b << endl; } } } return 0; }