How to take the Product of a List?

Question

I am trying to make a factorial calculator in C#, but I am having difficulties taking the product of all the numbers after I have collected them into a list.

        List<int> myList = new List<int>();

        Console.WriteLine("My Job is to take the factorial of the number you give");
        Console.WriteLine("What is the number?");
        string A = Console.ReadLine();
        int C = Convert.ToInt32(A);
        T:
        myList.Add(C);
        C--;

        if (C == 0) goto End;
        goto T;
    End:
        // This is where the problem is,
        // i don't know of a way to take to product of the list "myList"
        //Any Ideas?
        int total = myList.product();
        Console.WriteLine(" = {0}", total);
        Console.ReadLine();

That is how you can multiply http://stackoverflow.com/questions/19336150/how-to-multiply-all-elements-in-an-doubles-list , but you don't need that for factorial, also search for loops, and consider avoiding `goto`. — Habib, Jul 10 '15 at 15:36
Why would you add the input in a list in the first place? Also avoid using `goto` — Arthur Rey, Jul 10 '15 at 15:36
http://stackoverflow.com/questions/46586/goto-still-considered-harmful — Matt Burland, Jul 10 '15 at 15:38

score 0 · Answer 1 · answered Jul 10 '15 at 15:39

There doesn't seem to be much benefit in adding all the numbers to a list unless you need that for something.

As an alternative, something like this should work:

// set product to the number, then multiply it by every number down to 1.
private int GetFactorial(int number)
{
    int product = number; 
    for (var num = number - 1; num > 0; num--) 
    {
        product *= num;
    }
    return product;
}

score 0 · Accepted Answer · answered Jul 10 '15 at 15:43

You don't need a list to do a factorial:

Console.WriteLine("My Job is to take the factorial of the number you give");
Console.WriteLine("What is the number?");
int c = Convert.ToInt32(Console.ReadLine());
int total = 1;

for (int i = 2; i < c; i++)
{
    total *= i;
}

Console.WriteLine(total.ToString());
Console.ReadLine();

How to take the Product of a List?

2 Answers2