Problem that i cannot see

[anonymized]

There is a bug in the following program of insertion sort, value of 'n' changes during the process of swapping 2 a[] elements in insertion(). I cannot understand why,...
Please help.

#include <iostream>
#include <cstdlib>
using namespace std;

class Aray{

	public:
	int a[], n;

	Aray(int n){

		srand(time(0));
		this->n = n;

		for(int i = 0; i < n; i++){
			a[i] = rand()%n + 1;
		}

		cout << "unsorted Array is: " << endl;
		for (int i = 0; i < n; i++) cout << a[i] << "\t";
	}

	~Aray(){}

	void insertion(){
		for(int i = 0; i < n; i++){
			int min = i;

			for(int j = i; j < n; j++){
				if(a[min] > a[j]) min = j;
			}

				int temp = a[i];
				a[i] = a[min];
				a[min] = temp;

		}
	}

	void display(){
		for(int i = 0; i < n; i++){
			cout << a[i] << "\t";
		}
	}

	void tp(){cout << "number of elements: " << n << endl;}

};

int main(){

		int n;

		cout << "How many numbers do you want to sort?" << endl;
		cin >> n;

		Aray *b = new Aray(n);
		b->n = n;

		b->insertion();
		b->tp();

		cout << "\nThe sorted Array is: " << endl;
		b->display();


		return 0;
	}

[AoZplusplus]

Please refer to my comments.

#include <iostream>
#include <cstdlib>
#include <time.h>

using namespace std;

class Aray{
	public:
		//int a[] incomplete type is not allowed
		//I suspect that you have to specify the size of the array in class
		//Dynamic variable works fine, though, as I write below
	int n;
	int *a ;
	Aray(int n){
		a = new int[n];
		srand(time(0));
		this->n = n;
		for(int i = 0; i < n; i++)
		{
			a[i] = rand()%n + 1;
		}
		cout << "unsorted Array is: " << endl;
		for (int i = 0; i < n; i++) 
			cout << a[i] << "\t";
}
//Do you need this destructor that does nothing?
	~Aray(){}

	void insertion()
	{
		for(int i = 0; i < n; i++)
		{
			int min = i;
			for(int j = i; j < n; j++)
			{
				if(a[min] > a[j]) 
					min = j;
			}
			int temp = a[i];
			a[i] = a[min];
			a[min] = temp;
		}
	}
	void display()
	{
		for(int i = 0; i < n; i++)
		{
			cout << a[i] << "\t";
		}
	}

	void tp()
	{
		cout << "number of elements: " << n << endl;
	}
};

int main()
{

	int n;

	cout << "How many numbers do you want to sort?" << endl;
	cin >> n;

	Aray *b = new Aray(n);
	//Why do you need this now that you have initialized the Aray with n?
	b->n = n;
	b->insertion();
	b->tp();
	cout << "\nThe sorted Array is: " << endl;
	b->display();

	return 0;
}

[anonymized]

I just realised everything worked fine, when i put a[20]. You are right, i cannot put a[]...

Thank you very much for your prompt and perfect reply!

[AoZplusplus]

No problem! By the way, please mark this as solved. Thanks!
And remember to delete the array in destructor.