How to have a function return both index and value of an array?

Question

This function counts how often letter occur in a given string and puts that in an array (index is ascii-number of letter and value ist counted occurrences). Now I need to return both the letter (which it already does) and the value. Just by reading online I couldn't figure out how to use ref and alternatives to do that.

static char MostCommonLetter(string s)
    {
        int[] occurrances = new int[255];
        for (int i = 0; i < s.Length; i++)
        {
            if (char.IsLetter(s[i]))
            {
                int ascii = (int)s[i];
                occurrances[ascii]++;
            }
        }
        char maxValue = (char)Array.IndexOf(occurrances, occurrances.Max());
        return maxValue;
    }

dktaylor · Accepted Answer · 2018-06-03 18:46:53Z

4

In C# 7 and above, Value Tuples are your best bet. You could define your function as follows:

static (char letter, int occurrences) MostCommonLetter(string s)
{
    int[] occurrences = new int[255];
    for (int i = 0; i < s.Length; i++)
    {
        if (char.IsLetter(s[i]))
        {
            int ascii = (int)s[i];
            occurrances[ascii]++;
        }
    }
    char letter = (char)Array.IndexOf(occurrences, occurrences.Max());
    return (index: letter, occurrences: occurrences);
}

You could then reference the output like so:

var (index, occurrences) = MostCommonLetter(yourString);

answered Jun 3, 2018 at 18:46

dktaylor

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Comments

L_J · Accepted Answer · 2018-06-03 19:08:23Z

You can use the "out" parameter to return additional parameters from the function.

    static char MostCommonLetter(string s, out int maxOccurrance)
    {
        int[] occurrances = new int[255];
        for (int i = 0; i < s.Length; i++)
        {
            if (char.IsLetter(s[i]))
            {
                int ascii = (int)s[i];
                occurrances[ascii]++;
            }
        }

        maxOccurrance = occurrances.Max();
        char maxValue = (char)Array.IndexOf(occurrances, maxOccurrance);

        return maxValue;
    }

    //...

    // In C# 7 and above you can call it like that
    var c = MostCommonLetter("abccd", out int maxOccurrance);

    //// In older version of C# you should just declare out variable before use it
    //int maxOccurrance;
    //var c = MostCommonLetter("abccd", out maxOccurrance);

Luca Lindholm · Accepted Answer · 2018-06-03 19:30:52Z

0

The best and flexible way to do what you need in C# is by using a struct.

Define a struct in this way and use it to return multiple results at same time (a struct can even contain function… you can see those structs as lightier classes):

namespace YourApp.AnyNamespace {

    // Other things

    public struct SampleName
    {
        public char mostCommon;
        public int occurancies;
    }
}

answered Jun 3, 2018 at 19:30

Luca Lindholm

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2 Comments

Slaven Tojić Over a year ago

This for sure isn't "The best and flexible way"

Luca Lindholm Over a year ago

@SlavenTojić anyway, another user reminded about tuples, added in C# 7, that are even easier to use.

Slaven Tojić · Accepted Answer · 2018-06-03 19:49:31Z

0

An alternative solution would be using LINQ :

string str = "Hello World!";

var result = str.GroupBy(c => c)
                .Select(group => new { Letter = group.Key, Count = group.Count() })
                .OrderByDescending(x => x.Count)
                .First();

char letter = result.Letter;
int count = result.Count;

letter = 'l'

count = 3

edited Jun 3, 2018 at 19:49

answered Jun 3, 2018 at 19:13

Slaven Tojić

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2 Comments

Luca Lindholm Over a year ago

Ah yes, didn't read it… but now I can't delete the downvote, unless you edit the answer, says StackOverflow.

Luca Lindholm Over a year ago

Down Vote removed. I beg sorry. ;)

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