$[$Prob$.6.$ Fundamental of Programming$]$

$(15$p$)$ Answer for the following C$++$ program.

#include $$iostream$$

using namespace std;

class A $\{$

public:

virtual void foo$()\{$ cout $"$A$\_$foo$()"$ endl; $\}//$ same as printf$("$A$\_$foo$()\frac{?}{?}$

; in C

virtual void boo$()\{$ cout $"$A$\_$boo$()"$ endl; $\}$

$\}$;

class B: public A $\{$

public:

virtual void boo$()\{$ cout $"$B$\_$boo$()"$ endl; $\}$

virtual void zoo$()\{$ cout $"$B$\_$zoo$()"$ endl; $\}$

$\}$;

int main $()$

$\{$

B b;

b$.$foo$()$; b$.$zoo$()$;

$A**a1=$&$b$;

a$1->$foo$()$; a$1->$boo$()$; $/*$ HERE $*/$

$\}$

$($a$)$ Show the output of the above program $($there are four lines$).$

$($b$)$ For the output, which output line$($s$)$ correspond to a case where polymorphism,

overriding, and virtual function call occur all together? Explain briefly.

$($c$)$ If we add a statement a$1->$zoo$()$; at $/*$ HERE $*/$ in the above, can it be compiled

correctly? If so$,$ can it run correctly? If so$,$ what is its output? Explain briefly.

$(40$p$)$ Answer the following questions in two lines $($penalty if more than two lines$)$

$($a$)$ Pointers are tricky to use. Why do we need pointers in programming? That is$,$

what are pointers mainly used for in $\frac{C}{C}++$ programming?

$($b$)$ We can implement a Set using an array or a linked list. What is the advantage

of linked list compared to array? What is the disadvantage?