Question

I decided to solve the problem of finding given characters in a string. And I solved it in two ways:

The first(using hash-table to keep the values in ASCII for the chars we want to find):

static void Hash(string text, char[] charsToFind)
{
    Dictionary<int,char> chars = new Dictionary<int,char>();
    foreach (var letter in charsToFind)
    {
        chars[(int)letter] = letter;
    }

    foreach (var letter in text)
    {
        if (chars.ContainsKey((int)letter))
        {
            if (letter == chars[(int)letter])
            {
                Console.WriteLine("Element found at: {0}, value: {1}", (int)letter, letter);
            }
        }
    }
}

And the second way (the naive):

static void Naive(string text, char[] charsToFind)
{
    foreach (var letter in text)
    {
        foreach (var character in charsToFind)
        {
            if ((int)letter == (int)character)
            {
                Console.WriteLine("Element found at: {0}, value: {1}", (int)letter, letter);
            }
        }
    }
}

And everything works fine! The question I’d like to ask is which one is the better and if there are even better solutions to this problem?

Thanks in advance!

Answer 1

Using LINQ:

string input = "abc";
char[] charsToFind = new[] { 'a', '1', 'b' };
IEnumerable<int> ids = charsToFind.Select(ch => input.IndexOf(ch)); // { 0, -1, 1 }

---

With Hashset<T> which is generic hash table:

HashSet<char> set = new HashSet<char>(input.ToCharArray());
...