单项选择题用链表表示线性表的优点是____。
单项选择题有如下程序:#include<iostream>using namespace std;class Base{public:virtual void function1(){cout<< 0 ;}void function2(){out<< 1 ;}};class Derived:public Base{oublic:void function1(){cout<< 2 ;}void function2(){cout<< 3 ;}};int main(){Base*p=new Derived();p->function1(); p->function2();return 0;}运行时的输出结果是______。