在Int Array C＃中更改给定索引处的值

Question

I'm trying to create a process to count the frequency of each letter in a given input string. The code I have so far seems to work fine, except for updating the value of the int at a given index in the int array. When I debug the code it is successfully finding the index of the string array which corresponds to the character of the moment, so it appears that the problem is with the line: alphabetCount[index] = alphabetCount[index]++;

Here is the code.

    string[] alphabet = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"};
    int[] alphabetCount = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    string baseInput = string.Empty;

    private void button_count1_Click(object sender, EventArgs e)
    {
        baseInput = textBox_base.Text.ToUpper();
        int length = baseInput.Length;

        for (int i = 0; i < length; i++)
        {
            try
            {
                int index = Array.IndexOf(alphabet,baseInput[i].ToString());
                alphabetCount[index] = alphabetCount[index]++;
            }
            catch
            {
                //MessageBox.Show("nope");
            }
        }
    }

Answer 1

You can simplify the counter.

int[] alphabetCount =
    { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
string baseInput = string.Empty;

private void button_count1_Click(object sender, EventArgs e)
{
    baseInput = textBox_base.Text.ToUpper();

    foreach(var character in baseInput)
    {
        if(char.IsLetter(baseInput))
        {
            // A is ASCII 65, Z is ASCII 90
            // Subtract 65 to put it in the alphabetCount range
            var index = character - 65;
            alphabetCount[index]++;
        }
    }
}

Answer 2

The problem is alphabetCount[index]++ first assigns alphabetCount[index] and then increments the value. You need to use pre increment operator instead:

alphabetCount[index] = ++alphabetCount[index];

You can simply reproduce this behaviour like this:

var arr = new int[2];
arr[0] = arr[0]++;

Console.Write(arr[0]); // 0

Answer 3

You only have to write alphabetCount[index]++; or alphabetCount[index] = alphabetCount[index]+1; (equivalent)

or you use linq:

string words = "Hello World";
Dictionary<char, int> counted = words.ToUpper().GroupBy(ch => ch).OrderBy(g => g.Key).ToDictionary(g => g.Key, g => g.Count());