C＃中的数字总和

Question

I wrote I method which is suppose to recieve a nubmer from user and then check number from 0 to 1000. Then it should return all number which have digit sum equal to recieved number.
So if I enter 6, it should return numbers like 6, 42, 51, 33, 123 etc.
I'd really appreciate help since I've been dwelling on this for a while now.

public static double number() {
    Console.WriteLine("Enter your number! ");
    string enter = Console.ReadLine();
    double x = Convert.ToDouble(enter);        
    for (int i = 0; i < 1000; i++ ) {
        double r;
        double sum = 0;
        while (i != 0) {
            r = i % 10;
            i = i / 10;
            sum = sum + r;
        }
        if (sum == x) {
            Console.WriteLine(i + " ");
        }
    }
    return(0);
}

I am aware of the fact that there is a problem with "return(0)", but I'm not completely sure what exactly it is that this should be returning.

Answer 1

You are almost there: the only remaining problem is that you are modifying your loop counter i inside the nested while loop, which changes the workings of the outer loop.

You can fix this problem by saving a copy of i in another variable, say, in ii , and modifying it inside the while loop instead:

double r;
double sum = 0;
int ii = i;
while (ii != 0) {
    r = iCopy % 10;
    ii /= 10;
    sum = sum + r;
}

Answer 2

I'd suggest trying to do something like this:

public static IEnumerable<int> number()
{
    Console.WriteLine("Enter your number!");
    string enter = Console.ReadLine();
    int digitSum = int.Parse(enter);
    foreach (var n in Enumerable.Range(0, 1000))
    {
        if (n.ToString().ToCharArray().Sum(c => c - '0') == digitSum)
        {
            yield return n;
        }
    }
}

When I run this and enter 6 then I get this result: