Regex to match last character in string

Question

Suppose I have the following strings: cat I cat II cat III dog I dog III bird I

I would like to match all strings with a I, but NOT II or III.

So the correct match would give me:

cat I
dog I
bird I

I had the thought of matching an I with no other character after it, but perhaps there is a more direct way.

What would be the regex for such a pattern?

Answer 1

Try this sentence:

^(.*[^I])\I$

^ - begin of strings
(.*[^I]) - match any character other then 'I' ([^I] means "Do not catch 'I'")
\I - match an literal 'I'
$ - end of strings

Answer 2

You can use word boundaries, so the regex can be like this:

^.*\bI\b.*$

Regex demo

Answer 3

Try this one:

^[a-z|A-Z|0-9]+[^I]\s?I{1}$

I think this is a more accurate solution.

Try demo

Answer 4

This is a possible solution:

^.*\bI\b$

This could be used like this in C#:

Regex regex = new Regex(@"^.*\bI\b$");
var input = new string[]{"cat I","cat II","cat III","dog I","dog III","bird I"};
foreach(string text in input)
{
    if (regex.IsMatch(text))
        Console.WriteLine(text);
}