Need an better method of removing pattern within a string

Question

I have a method that to remove the description word base on the string, but I believe that there is more efficient way to do this.

The iMonster can be like fat orc rogue, and I want to remove the fat.

    private static string[] _adjectives = { "angry", 
                                            "big", 
                                            "fat", 
                                            "happy",
                                            "large", 
                                            "nasty", 
                                            "fierce", 
                                            "thin",
                                            "small", 
                                            "tall", 
                                            "short" };

    private static string RemoveMonsterAdjective(string iMonster)
    {
        foreach (string adjective in _adjectives)
        {
            if (iMonster.Contains(adjective))
            {
                iMonster = iMonster.Replace(adjective, "").Trim();
                break;
            }
        }
        return iMonster;
    }

hopefully someone can help me. Thanks in advance.

Your code looks OK. Only one thing: because of the break if the imonster is a "big fat nasty orc rogue" you will get "fat nasty orc rogue" as the result. — nemesv
– nemesv, Commented Jan 5, 2013 at 17:36
@lakedoo As long you manage your adjectives array, it seems fine. But you would need a way to elminitae multiple adjectives like removing multiple delimiters ;) +1 @nemesv — bonCodigo
– bonCodigo, Commented Jan 5, 2013 at 17:38
thanks, good point about multiple adjectives, I will fix that. — lakedoo
– lakedoo, Commented Jan 5, 2013 at 17:43
(relevant only if break is removed) String is immutable so if iMonster is big and _adjectives is large and could result in multiple hits it may help to use StringBuilder or StringBuffer to yield a heavily mutated result. Although it will increase complexity. — Yoztastic
– Yoztastic, Commented Jan 5, 2013 at 17:43

Sergey Kalinichenko · Accepted Answer · 2013-01-05 17:46:13Z

5

You can do all replacements in a single call using regular expressions, like this:

return Regex.Replace(
    iMonster,
    @"\b(angry|big|fat|happy|...)\b",
    ""
).Trim();

The idea behind this approach is to construct a regular expression that matches any adjective as a single word (so "bigot" would not be matched, while "big" would be matched), and replace that word with an empty string.

Here is a demo on ideone.

answered Jan 5, 2013 at 17:46

Sergey Kalinichenko

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4 Comments

ssube Over a year ago

I'd be interested to see a benchmark of this and the looping String.Replace. I would suspect that as the input gets longer and contains more adjectives, the regex is going to overcome its initial overhead and end up faster (less reallocation).

Sergey Berezovskiy Over a year ago

This solution leaves spaces which were between words

Konrad Rudolph Over a year ago

@lazyberezovsky Fair enough. ;-)

ssube Over a year ago

It seems that the regex, while simpler, is slower even for long strings: ideone.com/wWuexS

e_ne · Accepted Answer · 2013-01-05 18:07:16Z

4

Another possible short solution is:

var words = iMonster.Split(' ');
return string.Join(" ", words.Except(_adjectives));

I've done some profiling and compared the various solutions.

With input fat angry orc happy rogue and 1000000 iterations:

00:00:01.8457067 lakedoo
00:00:01.9772477 Eve
00:00:04.3859120 dasblinkenlight

Need to mention that I adapted dasblinkenlight's solution to have all the adjectives in the regex.

EDIT: corrected lakedoo's method by removing the break.

edited Jan 5, 2013 at 18:07

answered Jan 5, 2013 at 18:00

e_ne

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