Comparing strings and get the first place where they vary from eachother

Question

I want to get the first place where 2 string vary from each other. example: for these two strings: \"AAAB\" \"AAAAC\"

I want to get the result 4.

How do i d

Answer 1

string str1 = "AAAB";
string str2 = "AAAAC";

// returns the first difference index if found, or -1 if there's
// no difference, or if one string is contained in the other
public static int GetFirstDiffIndex(string str1, string str2)
{
    if (str1 == null || str2 == null) return -1;

    int length = Math.Min(str1.Length, str2.Length);

    for (int index = 0; index < length; index++)
    {
        if (str1[index] != str2[index])
        {
            return index;
        }
    }

    return -1;
}