藍橋杯題庫 BASIC-16 分解質因數

#include <iostream>
using namespace std;
int isprime(int n)
{
    if (n <= 1)
    {
        return 0;
    }
    else if (n == 2 || n == 3)
    {
        return 1;
    }
    else
    {
        for (int i = 2; i * i < n; i++)
        {
            if (n % i == 0)
            {
                return 0;
            }
        }
        return 1;
    }
}
int main()
{
    int a, b;
    cin >> a >> b;
    for (int i = a; i <= b; i++)
    {
        int temp = i;
        cout << i << "=";
        int flag = 0;
        while (temp != 1)
        {
            for (int j = 2; j <= temp; j++)
            {
                if (isprime(j) && temp % j == 0)
                {
                    temp = temp / j;
                    if (flag == 1)
                    {
                        cout << "*";
                    }
                    cout << j;
                    flag = 1;
                    break;
                }
            }
        }
        cout << endl;
    }
    return 0;
}