How to count the number of different digits in a number?

Question

This is a code that counts the number of digits in a number recursively. What can I add to this code to count how many different digits are in a number? Or maybe there is some other way?

    int numberOfDigits(int n)
    {
    if(n==0)
    return 0;
    else
    return numberOfDigits(n/10)+1;
    }

"This is a code that counts digits in a number." is incorrect. Voting to close as lacking reproducible example. — Cheers and hth. - Alf, Nov 26 '16 at 10:58
`return n.ToString().Distinct().Count(c => c >= '0' && c <= '9');` — Dmitry Bychenko, Nov 26 '16 at 12:14

score 2 · Accepted Answer · answered Nov 26 '16 at 11:10

Use sets!

static int NumberOfDigits(int a) {
    return new HashSet<char>(Math.Abs(a).ToString()).Count;
}

We make a into a string and then turn the string into a set of characters. Since sets cannot contain duplicate values, the count of the set is the number of distinct digits.

How to count the number of different digits in a number?

1 Answers1