A Problem & a Question for the "Composite" design pattern

[sidatra79]

I am trying to implement the composite "structural pattern". The attached code compiles but when I run the exe file the memory collapses.

Here is the code:

#include <iostream>
#include <iomanip>

class CTreeComponent {
public:
	virtual void traverse(int)=0;
};

class CTreeLeaf:public CTreeComponent {
public:
	CTreeLeaf(int wert):m_wert(wert){}
	void traverse(int tiefe){std::cout<<m_wert<<" ";}
private:
	int m_wert;
};

class CTreeComposite:public CTreeComponent {
public:
	CTreeComposite():m_anzahl(0) {}
	void add(CTreeComponent* elem){m_children[m_anzahl++]=elem;}
    void traverse(int tiefe){
		std::cout<<std::endl<<std::setw(tiefe*4)<<" "<<tiefe<<": ";
		for (int i=0;i<m_anzahl;i++)
			m_children[i]->traverse(tiefe+1);
	}
private:
	CTreeComponent* m_children[2];
	int m_anzahl;
};

	int main() {

		int i;
		CTreeComposite containers[99];
		for (i=0;i<4;i++) {
			containers[i].add(new CTreeLeaf(2*i));
			containers[i].add(new CTreeLeaf(2*i+1));
		}
		containers[2].add(&(containers[3]));
		containers[1].add(&(containers[2]));
		containers[0].add(&(containers[1]));
		containers[0].add(&(containers[2]));
		containers[0].add(&(containers[3]));
		for (i=3;i>=0;i--) {
			std::cout<<"Container"<<i<<" "<<": ";
			containers[i].traverse(1);
			std::cout<<std::endl;
		}

	}

The error output:
(Unhandled exception at 0x004011df in Kompositum.exe: 0xC0000005: Access violation writing location 0x0063deb0.)

Does anybody has any idea why?
I am not so experienced, so it might be sth simple.

Does anybody know any better way to implement such a design pattern?

Thanks in advance.

[mitrmkar]

You only have storage for two CTreeComponent pointers ... CTreeComponent* m_children[2]; the add(...) method could check that you are not using out of bounds indices.

[sidatra79]

Thanks a lot. I corrected it and the program now runs.

But what exactly do u mean with:

the add(...) method could check that you are not using out of bounds indices.

1.Could u/sbdy give me an example of how I could use the add method to perform this check?
2.Concerning memory and the "new" operators I used, which place would be the optimal one for using the "delete" operator to free up the memory?? The interior of a CTreeLeaf destructor or this of a CTreeComposite destructor???

[Alex Edwards]

void add(CTreeComponent* elem){
                         if(m_anzahl >= 0 && m_anzahl < 2)
                               m_children[m_anzahl++]=elem;
                         else std::cout << "ERROR! Element full." << std::endl;
             }