using System;

public class Program

{

    public static void Main()

    {

        var result = StrStr("my name is christian", "name");

        Console.WriteLine("result: " + result);

    }

    public static int StrStr(string haystack, string needle) {

        if (needle == null || needle == "")

            return 0;

        if (haystack == null || needle == "")

            return -1;

        if (needle.Length > haystack.Length)

            return -1;

        for (int i=0; i<=haystack.Length - needle.Length; i++) 

        {

            if (haystack[i] == needle[0])

            {

                Console.WriteLine(string.Format("i: {0}, j: {1}", i, haystack[i]));

                // use substring

                bool isSame = true;

                for (int j=1; j <needle.Length; j++)

                {

                    if (haystack[i+j]!=needle[j])

                    {

                        isSame = false; 

                        break;

                    }

                }

                Console.WriteLine(string.Format("isSame: {0}", isSame));

                if (isSame)

                    return i;

            }

        }

        return -1;

    }

}