Define the lowest and highest value among three numbers

Question

I’m trying to create a program in c# using windows Forms where it gets 3 numbers and tells me which is the biggest and which is the smallest, but I’m really very beginner and I don’t think where this error is, I already checked the list of errors of the IDE but this empty, it’s logic problem anyway. The code works but wrong.

Follow my code below:

        double n1 = 0;
        double n2 = 0;
        double n3 = 0;

        n1 = double.Parse(txtb1.Text);
        n2 = double.Parse(txtb2.Text);
        n3 = double.Parse(txtb3.Text);

        if (n1 > n2 && n1 > n3)
        {
            MessageBox.Show("O maior número é: " + n1);
        }

        else if (n1 > n2 && n1 < n3)
        {

        }

        else if (n1 < n2 && n1 < n3)
        {
            MessageBox.Show("O menor número é: " + n1);
        }

        else if (n2 > n1 && n2 > n3)
        {
            MessageBox.Show("O maior número é: " + n2);
        }

        else if (n2 > n1 && n2 < n3)
        {

        }

        else if (n2 < n1 && n2 < n3)
        {
            MessageBox.Show("O menor numero é: " + n2);
        }

        else if (n3 > n1 && n3 > n2)
        {
            MessageBox.Show("O maior número é: " + n3);
        }

        else if (n3 > n1 && n3 < n2)
        {

        }

        else if (n3 < n1 && n3 < n2)
        {
            MessageBox.Show("O menor numero é: " + n3);
        }

Answer 1

If I understand your problem from your comments is that your program only displays the largest or only the smallest and not both at the same time.

This is due to the fact that when using if with several else if only the first of them whose condition is true will be executed. In your case, more than one else if evaluates as true (one for the largest number and one for the smallest). A first alternative is to put everything as if since you’ve made all the possible combinations.

Another option is to use the library Math with the methods Maxand Min. Thus replacing your entire block if for:

MessageBox.Show("O maior número é: " + Math.Max(n1,Math.Max(n2,n3)));
MessageBox.Show("O menor numero é: " + Math.Min(n1,Math.Min(n2,n3)));

Answer 2

   double n1, n2, n3;

    n1 = double.Parse(txtb1.Text);
    n2 = double.Parse(txtb2.Text);
    n3 = double.Parse(txtb3.Text);

        if (n1 > n2 && n1 > n3)
        {
            MessageBox.Show("O maior número é: " + n1);
            if (n2 > n3) { MessageBox.Show("O menor número é: " + n3); } else { MessageBox.Show("O menor número é: " + n2); }

        }else
        {
            if (n2 > n1 && n2 > n3)
            {
                MessageBox.Show("O maior número é: " + n2);
                if (n1 > n3) { MessageBox.Show("O menor número é: " + n3); } else { MessageBox.Show("O menor número é: " + n1); }
            }

            else
            {                     
              MessageBox.Show("O maior número é: " + n3);
                if (n2 > n1) { MessageBox.Show("O menor número é: " + n1); } else { MessageBox.Show("O menor número é: " + n2); }
            }
        }

I did so because it is a small comparison between 3 numbers, if you have more numbers the recommended is to use the class Math with the methods Min and Max. Below I will leave the link to read the documentation about the class, if you are interested in knowing more. https://docs.microsoft.com/pt-br/dotnet/api/system.math?view=net-5.0

Answer 3

You can also use a list and sort it, but it is much slower depending on the case than compare with comparison operators.

// Declarando a lista
List<double> lista = new List<double>();

// Adicionando os valores à lista
lista.Add(double.Parse(txtb1.Text));
lista.Add(double.Parse(txtb2.Text));
lista.Add(double.Parse(txtb3.Text));

// Ordenando em ordem crescente
lista.Sort();

// Pegando o menor e o maior valor
double menor = lista[0]; // O primeiro da lista
double maior = lista[lista.Count - 1] // O último da lista

Answer 4

If I understand correctly, your program needs to display the lowest and highest value entered by the user. I believe a simple approach would be to create a vector (double[]) with the three numbers inserted and using the methods Min() and Max(), available on namespace System.Linq. The methods I mentioned are available for collections that implement the interface IEnumerable; return the lowest and highest value within a collection, respectively.

At the beginning of your file, enter the use of the mentioned namespace to access the methods:

using System.Linq;

So you can just call the method MessageBox.Show directly, without the need to check which number is larger/smaller or have to sort a list to do so, for example:

// criando um vetor de tamanho fixo, dado que precisa comparar apenas três números
double[] valoresInseridos = new double[3] { n1, n2, n3 };

MessageBox.Show($"Menor valor: {valoresInseridos.Min()}");
MessageBox.Show($"Maior valor: {valoresInseridos.Max()}");