ITP exceptions 1 first

#include <iostream>
#include <string>

using namespace std;

class LengthsNotEqualException : exception {
private:
    string message;

public:
    LengthsNotEqualException(string message) {
        this->message = message;
    }

    const char* what() const noexcept {
        return message.c_str();
    }
};

class Container {
private:
    int lenght;
    int* arr;

public:
    Container(int lenght) {
        this->lenght = lenght;
        arr = new int[lenght];
    }

    friend istream& operator >> (istream& cin, Container& container) {
        for (int i = 0; i < container.lenght; i++)
            cin >> container.arr[i];
        return cin;
    }

    friend int dot_product(Container& a, Container& b) {
        if (a.lenght != b.lenght)
            throw LengthsNotEqualException("The lengths of two containers are not equal");

        int c = 0;
        for (int i = 0; i < a.lenght; i++)
            c += a.arr[i] * b.arr[i];
        return c;
    }
};

int main()
{
    int size;
    cin >> size;
    Container a(size);
    cin >> a;

    cin >> size;
    Container b(size);
    cin >> b;

    try {
        cout << dot_product(a, b);
    }
    catch (LengthsNotEqualException & exception){
        cout << exception.what();
    }
    catch (exception & exception) {
        cout << exception.what();
    }
}