C# recursive method

Question

right now I am trying to practice recursion, but I got stuck. The objective is to to sum up all the digits of the number. For example method's signature takes one int parameter. This parameter is number (for example 123). And recursively i should sum up 1+2+3 , and give an answer of 6.

So far I tried :

(It probably does not make sense, but I tried a lot)

 public int sumofD(int n)
 {
         if (n == 0)
         { return 0; }
         else
         {
               return  n % 10 + sumofD(n-(n%10));
         }
 }

You should accept one answer

Thomas Ayoub
– Thomas Ayoub

2016-05-23 08:58:36 +00:00
Commented May 23, 2016 at 8:58 — Thomas Ayoub
– Thomas Ayoub, Commented May 23, 2016 at 8:58

Patrick Hofman · Accepted Answer · 2016-05-23 08:21:02Z

5

sumofD(n-(n%10)) makes 10 from n = 11 (11-(11%10) = 11-1 = 10). That will cause your recursive method to never end. You are not actually dividing anything, so the loop is endless.

Simply dividing with 10 will do the job here:

sumofD(n / 10)

answered May 23, 2016 at 8:21

Patrick Hofman

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Comments

Ranjit Singh · Accepted Answer · 2016-05-23 08:23:02Z

1

You are doing it wrong, n - (n%10) will make 123 to 123-3, i.e 120

public int sumofD(int n)
{
     if (n == 0)
     { return 0; }
     else
     {
           return  n % 10 + sumofD(n/10);
     }
}

edited May 23, 2016 at 8:23

answered May 23, 2016 at 8:19

Ranjit Singh

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2 Comments

Jamiec Over a year ago

And this is why just providing a fix to the code is a good, but not great, answer. You forgot to explain what they did wrong.

Ranjit Singh Over a year ago

Thanks, if someone will give me time to edit my answer then only I will :)

Aimnox · Accepted Answer · 2016-05-23 08:39:18Z

0

For what I understand you also need to sum the result if it's more than one digit.

So 99 will give you 9 (9+9=18, 8+1=9)

Then another way of doing it will be:

public int sumofD(int n)
{
    string str = n.ToString();
    int total = 0;
    foreach (char c in str.ToCharArray())
    {
        total += int.Parse(c+"");
    }
    if (total > 9) total = sumofD(total);
    return total;
}

If you just need the direct sum (99 give you 18) you can just delete the last if line.

answered May 23, 2016 at 8:39

Aimnox

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Comments

Huseyin Durmus · Accepted Answer · 2016-05-23 08:43:24Z

0

I rewrote function (sum of). I tried it is working

    public int sumofD(int n)
    {
        if (n == 0)
        { return 0; }
        else
        {
            return (n % 10 + sumofD(n / 10));
        }
    }

answered May 23, 2016 at 8:43

Huseyin Durmus

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