Xam's questions

I have the following class:

package menu;

import java.util.List;

public class Menu
{
   private String titulo;
   private List<String> opciones;

   public Menu(String titulo, List<String> opciones)
   {
       this.titulo = titulo;
       this.opciones = opciones;
   }

   public void mostrar()
   {
       System.out.println();
       System.out.println(titulo);    

       for (int i = 0; i < opciones.size(); i++)
       {
           System.out.println(i + 1 + ". " + opciones.get(i));
       }
       System.out.println();
    }
}

And in the method mainI have created two variables as you can see below:

import java.util.Arrays;
import java.util.List;
import menu.Menu;

public class Principal
{
  public static void main(String[] args)
  { 
    String tituloMenu = "Menú Principal";
    List<String> opcionesMenu = Arrays.asList("Jugar", "Ver instrucciones", "Salir");
   //resto del código
  }
}

My problem is that I am looking for an easier way to initialize the opcionesMenu. The way in which I initialize said variable was obtained by researching on SO, however I have not been able to conclude if it is possible ArrayListto initialize a C# style:

var opcionesMenu = new List<string> { "Jugar", "Ver instrucciones", "Salir" };

The other problem is that I don't understand very well how the initialization of the ArrayListone I put in the previous code works. Basically I have two questions: why is it necessary to use Arrays? and what exactly does it mean to make use of the method asList?

Thanks in advance for possible comments and/or answers.

Suppose we have the hypothetical case where pointers are used for all types of variables. More exactly, we have the following procedure to read the elements of a one-dimensional array:

void leer_arreglo(int *&v)
{
    int *i = new int;
    for (*i = 0; *i < dim_v; (*i)++)
    {
        cout << "Elemento " << *i + 1 << ": ";
        cin >> v[*i];
    }
    delete i;       
}

As you can see, even the variable i, which is only used to traverse the elements of the array, is declared as a pointer to int, and as such, at the end of the procedure the memory must be freed manually.

What would be the most reasonable solution to keep the variable iwithin the scope of the loop forwhile avoiding manually freeing the memory allocated for that pointer?

My first attempt was the following:

void leer_vector(int *&v)
{
    for (int *i = new int(0); *i < dim_v; (*i)++)
    {
        cout << "Elemento " << *i + 1 << ": ";
        cin >> v[*i];
    }
    delete i;       
}

The problem is that an error is generated at the moment of reaching the instruction delete i;because said variable no longer exists outside the scope of the for.

Then the following occurred to me:

void leer_vector(int *&v)
{
    for (int *i = new int(0); *i < dim_v; (*i)++)
    {
        cout << "Elemento " << *i + 1 << ": ";
        cin >> v[*i];
        delete i;
    }       
}

However, I seriously doubt that the above is a good idea because on each iteration I am freeing the allocated memory.

I didn't really know what to do until I discovered smart pointers ( thanks Paula_plus_plus) and then I got the following code:

void leer_vector(int *&v)
{
    for (auto i = make_unique<int>(); *i < dim_v; (*i)++)
    {
        cout << "Elemento " << *i + 1 << ": ";
        cin >> v[*i];
    }       
}

Nice, right? The variable iis in scope forand we don't have to worry about manually freeing the allocated memory. So my question arises: is this a valid use of smart pointers?

I ask this question because despite reviewing some SO links where it is analyzed in which cases this type of pointers should be used, I am still not entirely clear if in my particular case the last piece of code that I put is a correct solution and acceptable.

Thank you in advance for your comments and/or answers.

At the suggestion of the PaperBirdMaster user, I have decided to ask the question indicated in the title of this post.

Basically, as I mentioned to said user, I have seen in different SO answers that in C++ it is not necessary to include the instruction return 0;in the function mainsince the compiler is capable of including said instruction on its own. How much truth is there in the above statement?

Personally, I prefer to include the return 0;because it goes along the lines of using a returnwithin a function, since by definition functions return a value. It would be different if mainhe declared it as void main(), which is not standard, but at least it is valid in Visual Studio, for example, and there he would see the need to include some kind of return.

On the other hand, related to all of the above, how valid is it to use another type of returnlike, for example, return EXIT_SUCCESS;, which can be found in one of the books on C++ by Luis Joyanes.

Thanks in advance for your responses and/or comments.

A week ago I started studying the subject of pointers and dynamic arrays. As a practice, I have made the following program that allows the user to add two vectors of the size they want:

#include <iostream>
#include <iomanip>

using namespace std;

void leer_vector(int v[], int n)
{
    cout << "Ingrese los elementos del vector:\n\n";
    for (int i = 0; i < n; i++)
        cin >> v[i];
}

void escribir_vector(int v[], int n)
{
    cout << "Los elementos del vector son:\t\t";
    for (int i = 0; i < n; i++)
        cout << v[i] << setw(5);
}

void sumar_vectores(int v1[], int v2[], int v3[], int n)
{
    for (int i = 0; i < n; i++)
        v3[i] = v1[i] + v2[i];
}

int main()
{
    int dimension_vector;
    int *p_vector1, *p_vector2, *p_vector3;

    cout << "\250Cu\240ntos elementos desea ingresar?:\t";
    cin >> dimension_vector;
    cout << '\n';

    p_vector1 = new int[dimension_vector];
    p_vector2 = new int[dimension_vector];
    p_vector3 = new int[dimension_vector];

    leer_vector(p_vector1, dimension_vector);
    cout << '\n';
    leer_vector(p_vector2, dimension_vector);
    cout << '\n';
    escribir_vector(p_vector1, dimension_vector);
    cout << "\n\n";
    escribir_vector(p_vector2, dimension_vector);
    cout << "\n\n";

    p_vector3 = sumar_vectores(p_vector1, p_vector2, dimension_vector);
    escribir_vector(p_vector3, dimension_vector);
    cout << "\n\n";

    delete[] p_vector1;
    delete[] p_vector2;
    delete[] p_vector3; 

    system("pause");
    return 0;
}

My doubt is when defining the procedure void sumar_vectoresbecause I have used four parameters and I am not convinced to use that number of parameters. So, on the one hand, is it correct to use more than three parameters in a function/procedure? According to this answer , it should be avoided whenever more than three parameters can be used (that's how I understand the answer).

And if that were the case, how could I modify the procedure definition void sumar_vectoresso that it uses three or fewer parameters?

Thanks in advance for answers and/or comments.

Recently, I've been looking at various C++ code examples where you have something like the following:

//líneas de código
for (i = 0; i < n; i++)
{
   if((alguna_condición))
   {
      //más código
      break;
   }
}
//siguen más líneas de código

In my C++ classes I have only used the statement breakwith the conditional structure switchand so I was a bit surprised by the use of breakwith the repetitive structure for. Searching in Google I found the following links , however the only thing that I have achieved is to confuse me. From what I've read, for some breakthere's nothing wrong with using, but for others it's just as bad as using the infamous goto .

Basically my question, as the title suggests, is it okay to use breakin repetitive control structures, and if not, is it as "harmful" as using goto?.

Thanks in advance for comments and/or responses.

After having studied some library functions cctypelike isdigite, isalphaI decided to create a program, inspired by some tutorials I saw on yt, to validate integers.

Below my code:

#include <iostream> 
#include <string>
#include <cctype>

using namespace std;

bool tipo_i_valido(string s);
int capturar_i();

int main()
{
    int numero;

    numero = capturar_i();
    cout << "El numero ingresado es: " << numero << "\n" << endl;

    return 0;
}

bool tipo_i_valido(string s)
{
    int i, longitud_s;

    longitud_s = s.length();

    if (longitud_s == 1)
    {
        if (!isdigit(s[0]))     
            return 0;       
    }
    else
    {
        if (s[0] == '+' || s[0] == '-' || isdigit(s[0]) != 0)
        {
            for (i = 1; i < longitud_s; i++)
            {
                if (!isdigit(s[i]))             
                    return 0;
            }
        }
        else
            return 0;       
    }
    return 1;
}

int capturar_i()
{
    int n_numero;
    string numero;
    bool es_valido;

    do {
        cout << "Ingrese un numero:\t";
        getline(cin, numero);
        cout << "\n";

        es_valido = tipo_i_valido(numero);

        if (!es_valido)
            cout << "ERROR. Ingrese solo numeros enteros.\n" << endl;
    } while (!es_valido);

    n_numero = stoi(numero);

    return n_numero;
}

As you can see, what I do is enter a string and if it turns out to be an integer including the sign, for example, +24or -12, then it considers it valid and the program converts the string using stoi. My problem is that for some reason in VS 2017, when I run my program, if I put the character ñthe program crashes and I get the following message: "debug assertion failed [...]". However, the code above, after compiling it to Dev C++ 5.11, runs as normal when executed.

Why is it that in VS the character ñcrashes my program, but in Dev C++ it doesn't?

Thanks in advance for your responses and/or comments.

I'm making an options menu using do whilequite simple, but after watching some videos on yt I decided to try the so-called "options menu with arrows", where there is an arrow of the shape ==>that points to each option in the menu and that scrolls using the arrow keys on the keyboard.

In the videos I saw the library conio.hor a variant is used conio2.h. The authors of the videos use this library to be able to call the function getch()that, as I understood, is used to use the directional arrows.

In one of the videos, for example, the following is done:

#define TECLA_ARRIBA 72
#define TECLA_ABAJO 80
#define ENTER 13

// acá va el código del menú

do
        {
            tecla = getch();
        }
        while(tecla != TECLA_ARRIBA && tecla != TECLA_ABAJO && tecla != ENTER);

My question is that I don't know if it's correct to use libraries like conio.hor conio2.hbecause I read on certain websites that these libraries are deprecated, in addition to the fact that their use is a bad practice in C++.

And so I was wondering how you can use directional arrows in C++ without using such libraries. On the other hand, I have tried one of the programs that I saw in VS 2017 and if it compiles, as long as it changes getch()to _getch(). Does this imply that there is no problem using the library conio.hin VS, or should using such a library be avoided anyway?

Thank you in advance for your comments and/or answers.

I have made the following program that calculates the inheritance based on the number of children:

#include <iostream>

using namespace std;

int leer_datoi()
{
    int dato;

    cin >> dato;

    return dato;    
}

double leer_datod()
{
    double dato;

    cin >> dato;

    return dato;
}

void calcular_herencia()
{
    double herencia, mayor;
    int num_hijos;

    do{
    cout << "Ingrese el importe de la herencia:\t";
    herencia=leer_dato_d();
    cout << "\n";

    if(herencia<=0)
        cout << "ERROR. Ingrese una cantidad positiva\n" << endl;
   } while(herencia<=0);

   do{
      cout << "Ingrese la cantidad de hijos:\t\t";
      num_hijos=leer_dato_i();
      cout << "\n";

      if(num_hijos<=0)
        cout << "ERROR. Ingrese una cantidad positiva\n" << endl;
  } while(num_hijos<=0);

    if(num_hijos<=4)
    {
        herencia=herencia/num_hijos;
        cout << "La herencia para cada hijo es:\t\t" << herencia << "\n" << endl;
    }
    else
    {
        mayor=herencia/2;
        herencia=mayor/(num_hijos-1);
        cout << "La herencia para el hijo mayor es:\t" << mayor << "\n" << endl;
        cout << "La herencia para el resto de hijos es:\t" <<  herencia << "\n" << endl;
    }
}

int main()
{
    calcular_herencia();    

    return 0;
}

I tried it and it works normal. Then, out of curiosity, I put a non-integer value when entering the number of children (let's say 4.5) and the program still worked, which seems strange to me since the variable num_hijosis of integer type.

My question is:

What is this about?