Knowing when my list is coming with values in sequence

Question

I have a List<int>:

[2,3,5,4,6]

Although not in order, it is a sequence of numbers (2,3,4,5,6) How do I validate this?

Note: There will always be 5 positions and the numbers will be from 1 to 6

Answer 1

You can use the SequenceEqual next to the OrderBy. Supposing your list calls lista, see how it would look:

lista.SequenceEqual(lista.OrderBy(x => x))

This line will return a Boolean saying whether it is ordered or not.

See working on Dotnetfiddle.

Answer 2

You can use the following function:

public bool hasNumberSequence(List<int> numbers)
{
    numbers.Sort();

    int numerosSequenciais = 0;

    for (int i = 1; i < numbers.Count(); i++)
    {
        if (numbers[i] != (numbers[i - 1] + 1))
            numerosSequenciais = 0;
        else
            numerosSequenciais++;
    }

    return numerosSequenciais >= 4;
}

This function returns true in case there is a sequence of at least 4 numbers in the list of int and false if there is no.

Examples of Use

List<int> numeros = new List<int>() { 0, 3, 5, 4, 6 };
Console.WriteLine(hasNumberSequence().ToString(numeros)); // True

numeros = new List<int>() { 2, 3, 5, 4, 6 };
Console.WriteLine(hasNumberSequence(numeros).ToString()); // True

numeros = new List<int>() { 2, 1, 0, 4, 6 };
Console.WriteLine(hasNumberSequence(numeros).ToString()); // False