stack concept with array of object in C++ - c++

Question

#include<iostream.h>
using namespace std;
class staticdemo
{
static int rollno;
string name;
public:
staticdemo()
{
cout<<"NAME: ";
getline(cin,name);
rollno++;
}
int getname()
{
cout<<name;
return 0;
}
static int getvalu()
{
return rollno;
}
};
int staticdemo::rollno=10;
int main()
{
int i,n;
cout<<"enter the number of studentd:";
cin>>n;
staticdemo s[n];
for(i=0;i<n;i++)
{
cout<<"name:"<<s[i].getname();
cout<<"\nroll no: "<<s[i].getvalu();
}
system("pause");
return 0;
}
I learning C++, i have a doubt in stack with array of object concept,
in my above program i get the names from user and rollno incremented through stack
while i retrieving list back it will give finally updated stack value, how to get the fully updated rollno values, (how to display the unique rollno for every names),
pls post your valuable solution

Answer 1

If I'm reading your question correctly, you want the rollno variable to be unique for each instance of the staticdemo class? Well then you can't have the member as static, because static members are shared among all instances of a class.

Answer 2

I think I roughly understand your question, although it seems a bit hard to get what you need.
What you have done is partially right, you use a static member variable "rollno" to record the count, however, if you really want what you need, you will need another non-static variable to record the index, e.g:
class staticdemo {
static int rollnoGlobal; // this will record the global count, used by everybody
int myRollno; //Non-static, this will record the rollno index for this particular object
string name;
public:
staticdemo() {
cout<<"NAME: ";
getline(cin,name);
myRollno = rollnoGlobal; // This is the step for each individual to remember its index
rollnoGlobal++;
}
int getname() {
cout<<name;
return 0;
}
static int getGlobalRollnoValue() {//return the global count;
return rollnoGlobal;
}
int getMyRollno() { // return the index or you call it rollno for this particular object
return myRollno;
}
};
int staticdemo::rollnoGlobal=10;
int main() {
int i,n;
cout<<"enter the number of studentd:";
cin>>n;
staticdemo s[n];
for(i=0;i<n;i++)
{
cout<<"name:"<<s[i].getname();
cout<<"\nroll no: "<<s[i].getMyrollno();
}
system("pause");
return 0;
}
Again if I was correct, the problem you faced is more like a understanding of static member variable and methods in C++ classes. This example you need two things:
A unique index for each variable, this is done by your original rollno static member.
Each staticdemo object must store its unique index. And this is the step you missed. After the global count increased, it increased for everybody because it is static. If you need to store it for each individual, you need another non-static member.
Side notes:
STACK is a very specific programming concept as pointed out by others, you question obviously does not need stack. You can try google what is a stack in programming.