质数因子求法

方法1：

long int input;while (cin>>input){while (input!=1){for (int i = 2; i <= input; ++i){if (input%i == 0){input /= i;cout << i << ' ';break;}}}}

方法2：

long int input;while (cin>>input){for (int i = 2; i <= input; ++i){if (input%i == 0){input /= i;cout << i << ' ';i = 1;}}}

方法3：

long int input;while (cin>>input){for (int a = 2; a <= sqrt(input); a++){while (input%a == 0){cout << a << ' ';input = input / a;}}if (input>1) cout << input << ' ';}