Hey my code is giving segmentation error. Can someone help me out with

Question

Hey my code is giving segmentation error. Can someone help me out with it

using namespace std;

template<typename t>
class hello
{
private:
    t *a;
    t *b;
    t *c;
    int size;
public:

    hello()
    {
        size = 0;
        a = new t[100];
        b = new t[100];
        c = new t[100];
    }
    hello(int s)
    {
        size = s;
        a = new t[size];
        b = new t[size];
        c = new t[2 * size];
        cout << "Enter the contents of the array" << endl;
        for (int i = 0; i < size; i++)
        {
            cin >> a[i];
        }
        cout << "Enter the contents of the array" << endl;
        for (int j = 0; j < size; j++)
        {
            cin >> b[j];
        }
    }
    void unionn()
    {
        for (int i = 0; i < size; i++)
        {
            c[i] = a[i];
        }
        for (int i = 0; i < size; i++)
        {
            c[size] = b[i];
            size++;
        }
        for (int i = 0; i < (2*size); i++)
        {
            cout << c[i];
        }
    }
};

int main()
{   
    int length;
    cout<<"Enter the length of the array"<<endl;
    cin>>length;
    cout<<"Enter the integer contents of the array"<<endl;
    hello <int>c1(length);
    c1.display();
    c1.unionn();
    cout<<"Enter the string contents of the array"<<endl;
    hello <string>c2(length);
    c2.display();
    c2.unionn();
    return 0;
}