Counting vowels using switch

Question

I'm new to C#. While learning it, I tried to design a program which count the vowels in a sentence.

In my code, I used the "foreach" statement with the if-else if statement. I would like to convert these line of code using the switch statement but I'm not really sure where to go. Do I need to add a new method? I would appreciate your help.

This is what I tried so far: I checked this one is very wrong. The "case 1" for example needs to have a constant. I'm not sure what constant shall I use here.

foreach (char v in yourSentence)
{
    switch (v)
    {
    case 1: 
        (v==ch1); 
      counta++; 
     j++; 
     break;

    case 2: 
     (v==ch2); 
     counte++; 
     j++; 
     break;
    case 3: 
     (v==ch3); 
     counti++; 
     j++; 
     break;
    case 4: 
     (v==ch4); 
     counto++; 
     j++; 
     break;
    case 5: 
     (v==ch3); 
     counti++; 
     j++; 
     break;             
    }
}

Another question: I tried to change the color of the display text in the listBox. Is that possible to have different colors? What I also tried here is the first 5 (listBox1.Items.Add) are violet. And the sum of the (listBox1.Items.Add) is blue. But it seems that it didn't change. Did I miss something here?

private void btnCount_Click(object sender, EventArgs e)
{
    string yourSentence;
    yourSentence = textBoxVowels.Text.ToLower().Trim();

    char ch1 = 'a';
    char ch2 = 'e';
    char ch3 = 'i';
    char ch4 = 'o';
    char ch5 = 'u';

    int counta = 0;
    int counte = 0;
    int counti = 0;
    int counto = 0;
    int countu = 0;

    int j = counta + counte + counti + counto + countu;



    foreach (char v in yourSentence)
    {
        if (v == ch1) { counta++; j++; }

        else if (v == ch2) { counte++; j++; }

        else if (v == ch3) { counti++; j++; }

        else if (v == ch4) { counto++; j++; }

        else if (v == ch5) { countu++; j++; }
    }

    listBox1.Items.Add("There are " + counta.ToString().Trim() + " a's in the sentence");
    listBox1.Items.Add("There are " + counte.ToString().Trim() + " e's in the sentence");
    listBox1.Items.Add("There are " + counti.ToString().Trim() + " i's in the sentence");
    listBox1.Items.Add("There are " + counto.ToString().Trim() + " o's in the sentence");
    listBox1.Items.Add("There are " + countu.ToString().Trim() + " u's in the sentence");
    listBox1.Font = new Font("Arial", 12, FontStyle.Bold);
    listBox1.ForeColor = Color.Violet;

    listBox1.Items.Add("There are " + j.ToString().Trim() + " vowels in the sentence");
    listBox1.ForeColor = Color.Blue;
}


private void btnClear_Click(object sender, EventArgs e)
{
    textBoxVowels.Text = null;
    listBox1.Items.Clear();
}

====

@Noldorin: I tried the code you gave and it seems it didn't work. did I miss something here:

  public static int CountVowels(string value)
    {
        char ch1 = 'a';
        char ch2 = 'e';
        char ch3 = 'i';
        char ch4 = 'o';
        char ch5 = 'u';

        int counta = 0;
        int counte = 0;
        int counti = 0;
        int counto = 0;
        int countu = 0;


        const string vowels = "aeiou";
        return value.Count(chr => vowels.Contains(char.ToLower(chr)));
        int j = counta + counte + counti + counto + countu;

        //listBox1.Items.Add("There are " + j.ToString().Trim() + " vowels in the sentence");
    }

==========

The switch statement is working fine now. Thanks for the hint. Now I recalled that I have to use a constant value.

Thanks to dahlbyk. Maybe I'll try it and see if it works.

Does anybody have any idea what event I'll use if I want to display the number of vowels while writing?

Thanks again

Answer 1

Or just simplify the whole problem by using a bit of LINQ. :)

public static int CountVowels(this string value)
{
    const string vowels = "aeiou";
    return value.Count(chr => vowels.Contains(char.ToLower(chr)));
}

The Count extension method is particularly well suited to this task. Also, notice the use of a string of all vowels to check each character - much simpler than a switch statement.

Note: It seems I missed the fact that you want to count each vowel individually. In this case, the LINQ becomes a bit more complicated (at least if you want to do it efficiently), but I shall leave that as an exercise for you. Regardless, a switch statement is probably a good way to learn the basics of C#.

---

Since you're probably curious about the switch statement anyway, the following code uses the correct syntax:

foreach (var chr in sentence)
{
    switch (chr) 
    {
        case 'a':
            ...
            break;
        case 'e':
            ...
            break;
        case 'i':
            ...
            break;
        case 'o':
            ...
        case 'u':
            ...
            break;
     }
}

Answer 2

I think you misunderstood how 'switch/case' works. Just change them to this:

case 'a': 
     counta++; 
     j++; 
     break;

Case needs a constant value that should be compared to the current character.

Answer 3

Please also check the other answers to your questions for many helpful tips. I'm just rewriting your first piece of example code from your question to probably let it do what you mean:

foreach (char v in yourSentence)
{
    switch (v)
    {
        case 'a': counta++; j++; break;
        case 'e': counte++; j++; break;
        case 'i': counti++; j++; break;
        case 'o': counto++; j++; break;
        case 'u': countu++; j++; break;
    }
}

You seem to want to increase one of the { counta, counte, counti, counto, countu } variables for the five specific vowels using the switch (right?) and also increase the j variable for each of the vowels.

Having given this answer, I would personally do something different altogether. Like the LINQ example given by Noldorin. Or something like this, as perhaps suggested by cherryalpha:

// create dictionary
var counts = new Dictionary<char,int>();

// initialize it for the vowels
foreach (char v in "aeiuo")
{
    counts.Add(v, 0);
}

// count all characters in sentence
foreach (char v in yourSentence) {
    if ( counts.ContainsKey(v) ) {
        // increase count for known characters
        counts[v]++;                        
    } else {
        // add new count for characters not seen previously
        counts.Add(v,1);
    }
}

// calculate your total number of vowels
j = counts['a'] + counts['e'] + counts['i'] + counts['o'] + counts['u'];

Quick warning, just in case: You would need a using System.Collection.Generic at the top of your source file that contains this code to make sure the generic Dictionary is known by its short name.

(And be aware that this code will not only give you vowel counts, but counts for all the other characters in yourSentence as well.)

Answer 4

Here's a more advanced solution:

public static Dictionary<char, int> CountLetters(string value, string letters)
{
    var counts = letters.ToDictionary(c => c.ToString(), c => 0, StringComparer.OrdinalIgnoreCase);

    var groups = from c in value
                 let s = c.ToString()
                 where counts.ContainsKey(s)
                 group s by s;

    foreach(var g in groups)
        counts[g.Key] = g.Count();

    return counts;
}

Which you could use like this:

var letterCounts = CountLetters(yourSentence, "aeiou");

int countA = letterCounts["a"];
int countE = letterCounts["e"];
int countI = letterCounts["i"];
int countO = letterCounts["o"];
int countU = letterCounts["u"];

int total = countA + countE + countI + countO + countU;

Update: Just realized that a StringComparer won't work for char keys. Switching to string key - not as efficient as char, but easier than writing a case-insensitive char comparer. I prefer the comparer approach to doing some sort of ToLower/ToUpper on everything dictionary-related.

Answer 5

I wrote a method that returns a Dictionary:

    public Dictionary<char,int> CountVowels(string sentance)
    {
        const string vowels = "aeiou";

        Dictionary<char,int> dic = new Dictionary<char, int>();

        foreach (char c in vowels)
            dic.Add(c, sentance.Count(chr => c == chr));

        return dic;
    }

Answer 6

const string VOWELS = "aeiou";
var str = "Lorem ipsum dolor sit amet";
var q = from ch in str
        where VOWELS.Contains(ch)
        group ch by ch into g
        select g;
var dict = q.ToDictionary(_ => _.Key, _ => _.Count());