Substring algorithm

Question

Can someone explain to me how to solve the substring problem iteratively?

The problem: given two strings S=S₁S₂S

Answer 1

I know I'm late to the game but here is my version of it (in C#):

    bool isSubString(string subString, string supraString)
    {
        for (int x = 0; x <= supraString.Length; x++)
        {
            int counter = 0;
            if (subString[0] == supraString[x]) //find initial match
            {
                for (int y = 0; y <= subString.Length; y++)
                {
                    if (subString[y] == supraString[y+x])
                    {
                        counter++;
                        if (counter == subString.Length)
                        {
                            return true;
                        }
                    } 
                }
            }
        }
        return false;
    }