质数因子

功能：输入一个正整数按从小到大输出它的所有质数因子，如180（2，2，3，3，5）

void hwOJ(){    int x = 1802;    int len = x/2 ;    vector<int> a, b;    bool flag;    for (int i = 2; i < len; ++i){        flag = true;        for (int j = 2; j <= i/ 2; ++j){            if (i%j == 0){ flag = false; break; }        }        if (flag)            a.push_back(i);    }    cout << a.at(0) << endl;    while (x > 0){        for (int i = 0; i < a.size(); ++i){            if (x%a.at(i) == 0){            cout <<a.at(i) << " ";                x = x / a.at(i);                break;            }        }    }    cout << endl;}