Fastest way to remove chars from string

Question

I have a string from which I have to remove following char: \'\\r\', \'\\n\', and \'\\t\'. I have tried three different ways of removing these char and benchmarked them so I

Answer 1

Here's the uber-fast unsafe version, version 2.

    public static unsafe string StripTabsAndNewlines(string s)
    {
        int len = s.Length;
        char* newChars = stackalloc char[len];
        char* currentChar = newChars;

        for (int i = 0; i < len; ++i)
        {
            char c = s[i];
            switch (c)
            {
                case '\r':
                case '\n':
                case '\t':
                    continue;
                default:
                    *currentChar++ = c;
                    break;
            }
        }
        return new string(newChars, 0, (int)(currentChar - newChars));
    }

And here are the benchmarks (time to strip 1000000 strings in ms)

    cornerback84's String.Replace:         9433
    Andy West's String.Concat:             4756
    AviJ's char array:                     1374
    Matt Howells' char pointers:           1163

Answer 2

Even faster:

public static string RemoveMultipleWhiteSpaces(string s)
    {
        char[] sResultChars = new char[s.Length];

        bool isWhiteSpace = false;
        int sResultCharsIndex = 0;

        for (int i = 0; i < s.Length; i++)
        {
            if (s[i] == ' ')
            {
                if (!isWhiteSpace)
                {
                    sResultChars[sResultCharsIndex] = s[i];
                    sResultCharsIndex++;
                    isWhiteSpace = true;
                }
            }
            else
            {
                sResultChars[sResultCharsIndex] = s[i];
                sResultCharsIndex++;
                isWhiteSpace = false;
            }
        }

        return new string(sResultChars, 0, sResultCharsIndex);
    }

Answer 3

Looping through the string and using (just one) StringBuilder (with the proper constructor argument, to avoid unnecessary memory allocations) to create a new string could be faster.

Answer 4

I believe you'll get the best possible performance by composing the new string as a char array and only convert it to a string when you're done, like so:

string s = "abc";
int len = s.Length;
char[] s2 = new char[len];
int i2 = 0;
for (int i = 0; i < len; i++)
{
    char c = s[i];
    if (c != '\r' && c != '\n' && c != '\t')
        s2[i2++] = c;
}
return new String(s2, 0, i2);

EDIT: using String(s2, 0, i2) instead of Trim(), per suggestion

Answer 5

String.Join(null, str.Split(new char[] { '\t', '\r', '\n' },
    StringSplitOptions.None));

might give you a performance increase over using Aggregate() since Join() is designed for strings.

EDIT:

Actually, this might be even better:

String.Concat(str.Split(new char[] { '\t', '\r', '\n' },
    StringSplitOptions.None));

Answer 6

try this

string str = "something \tis \nbetter than nothing";
string removeChars = new String(new Char[]{'\n', '\t'});
string newStr = new string(str.ToCharArray().Where(c => !removeChars.Contains(c)).ToArray());