Pulling/adding specific values out of an array using a for-loop

Question

The background of this program is simple enough: I want a user to be able to enter any letter (A, B, C, etc.) into a textbox, and with the click of a button, have the program return how many U.S. states begin with that letter (e.g. letter A entered and result is 4).

Here is my code as of now...

 private void btnClick_Click(object sender, EventArgs e)
        {
    string[] States = new String[50] {"Alabama", "Alaska", "Arizona", "Arkansas", "California", "Colorado",
        "Connecticut", "Delaware", "Florida", "Georgia", "Hawaii", "Idaho", "Illinois", "Indiana", "Iowa", "Kansas",
        "Kentucky", "Louisiana", "Maine", "Maryland", "Massachusetts", "Michigan", "Minnesota", "Mississippi", "Missouri", 
        "Montana", "Nebraska", "Nevada", "New Hampshire", "New Jersey", "New Mexico", "New York", "North Carolina", 
        "North Dakota", "Ohio", "Oklahoma", "Oregon", "Pennsylvania", "Rhode Island", "South Carolina", "South Dakota", 
        "Tennessee", "Texas", "Utah", "Vermont", "Virginia", "Washington", "West Virginia", "Wisconsin", "Wyoming"};

        string myLetter = txtboxEnter.Text;
        int result;
        result = 0;

        for (int i = 0; i <= States.Length - 1; i++)
        {
            if (States[i].Substring(0, 1) == myLetter)
            {
                result = result + i;
            }
            else
            {
                result = 0;
            }
        }
        lblDisplay.Text = Convert.ToString(result);
    }

As you see, I have the States declared in an array.

The issue I am having is with the for loop and the If statement inside it.

The value always returned is 0. I feel as though I need another line of code directly for the loop to total values. Am I correct?

Cory Nelson · Accepted Answer · 2013-10-02 21:43:43Z

4

Change this:

if (States[i].Substring(0, 1) == myLetter)
{
    result = result + i;
}
else
{
    result = 0;
}

To this:

if (States[i].Substring(0, 1) == myLetter)
{
    ++result;
}

And if you want to make things a bit more efficient, change that comparison to this:

if (States[i].StartsWith(myLetter))

answered Oct 2, 2013 at 21:43

Cory Nelson

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1 Comment

Papa Burgundy Over a year ago

yes and you also may want to make sure it is case insensitive. You can overload StartsWith to handle case how you prefer.

Ben Smith · Accepted Answer · 2013-10-02 23:30:56Z

3

Linq could be used for a more eloquent solution i.e. use:

States.Count(state => state.StartsWith(myLetter));

instead of your "for" loop.

edited Oct 2, 2013 at 23:30

answered Oct 2, 2013 at 21:55

Ben Smith

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3 Comments

Cory Nelson Over a year ago

+1, this is what I'd do too. Did not want to conflate logic error correction with full algorithm replacement.

Papa Burgundy Over a year ago

Nice. Adding case handler and trimming TextBox... States.Count(state => state.Substring(0, 1).ToUpper() == myLetter.Trim().ToUpper());

Ben Smith Over a year ago

@CoryNelson I agree that you answered the problem, though when I see questions like this I always feel that Linq delivers cleaner code as opposed to this laboured for loop!

Kevin T · Accepted Answer · 2013-10-02 22:36:52Z

If all you're doing is finding the number of states that start with each letter, I wouldn't use this kind of solution, since the data is basically static. You could do a table lookup instead using a Dictionary<char, int> and work with single characters instead of strings, and make it a class variable so you don't have to create it every time. For example:

//-snip-
private Dictionary<char, int> States;

//-snip-
public Form1()
{
    States = new Dictionary<char, int>();
    States.add('A', 4);
    States.add('B', 0);
    States.add('C', 3);
    States.add('D', 1);
    //... etc.
}
//-snip-

private void btnClick_Click(object sender, EventArgs e)
{
    char myLetter = txtboxEnter.Text.Trim()[0]; // do some other input sanitation here
    int result = States[myLetter];
    lblDisplay.Text = Convert.ToString(result); // consider making your Dictionary <char, string> so you can skip the conversion here
}

And if you still insist on your solution, you can also add some performance tweaks to it by taking advantage of the fact that your array is sorted. You could do a binary search but that's kind of overkill, but at least you could break out of your loop once you have found a state matching the criteria and then a state that no longer matches the criteria (e.g. if you're looking for all words in the English dictionary starting with B, you would stop once you hit a word starting with C).

gmtek · Accepted Answer · 2013-10-02 23:21:51Z

0

Using Lambda

result = Array.FindAll(States, x => x.StartsWith(myLetter)).Length;

answered Oct 2, 2013 at 23:21

gmtek

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