Question

I want to find the position of a substring in a string if present without using any string method including indexof. I tried so much times but failed. Will anybody tell me how to do in C#? We can use .Length operator.

Answer 1

Sorry.. thought this would be a fun exercise for me, so…

Spoiler

class Program
{
    static void Main(string[] args)
    {
        string str = "abcdefg";
        string substr = "cde";
        int index = IndexOf(str, substr);
        Console.WriteLine(index);
        Console.ReadLine();
    }

    private static int IndexOf(string str, string substr)
    {
        bool match;

        for (int i = 0; i < str.Length - substr.Length + 1; ++i)
        {
            match = true;
            for (int j = 0; j < substr.Length; ++j)
            {
                if (str[i + j] != substr[j])
                {
                    match = false;
                    break;
                }
            }
            if (match) return i;
        }

        return -1;
    }
}