What's the best way to remove strings?

Question

I need ideas with the best performance to remove/filter strings

I have:

string Input = "view('512', 3, 159);";

What's the best performance way to remove "view(" and ");" and the quotes? I can do this:

Input = Input.Replace("view(","").Replace("'","").Replace("\"","").Replace(");","");

but it seems rather inelegant.

Input.Split('(')[1].Split(')')[0].Replace("'", "");

it seems rather better

I want no do it by using regular expression; I need make the faster application what I can. Thanks in advance! :)

Regex is possibly faster in this case... Do you need to deal with nested parentheses? — Ben Voigt
– Ben Voigt, Commented Jul 11, 2011 at 22:15
@Freed:to best performance @Frédéric Hamidi:yes,response updated — The Mask
– The Mask, Commented Jul 12, 2011 at 2:47

Brandon Moretz · Accepted Answer · 2011-07-11 22:54:44Z

You could use a simple linq statement:

string Input = "view('512', 3, 159);"; string output = new String( Input.Where( c => Char.IsDigit( c ) || c == ',' ).ToArray() );

Output: 512,3,159

If you want the spaces, just add a check in the where clause.

Guffa · Accepted Answer · 2011-07-11 22:14:40Z

You could use just a Substring to remove the view( and );:

Input.Substring(5, Input.Length - 7)

Other than that it looks reasonably efficient. Plain string operations are pretty well optimised.

So:

Input = Input.Substring(5, Input.Length - 7) .Replace("'", String.Empty) .Replace("\"", String.Enmpty);

Ben Voigt · Accepted Answer · 2011-07-11 22:18:03Z

char[] Output = Input.SkipWhile(x => x != '(') // skip before open paren .Skip(1) // skip open paren .TakeWhile(x => x != ')') // take everything until close paren .Where(x => x != '\'' && x != '\"') // except quotes .ToArray(); return new String(Output);

Arjun Shetty · Accepted Answer · 2011-07-12 08:18:48Z

2

Hope this helps

Regex.Replace("view('512', 3, 159);",@"[(view)';]","")

answered Jul 12, 2011 at 8:18

Arjun Shetty

1,5851 gold badge15 silver badges36 bronze badges

Comments

agent-j · Accepted Answer · 2011-07-11 22:15:44Z

IndexOf, LastIndexOf, and Substring are probably fastest.

string Input = "view('512', 3, 159);"; int p1 = Input.IndexOf('('); int p2 = Input.LastIndexOf(')'); Input = Input.Substring (p1 + 1, p2 - p1 - 1);

Peter O. · Accepted Answer · 2011-07-11 22:20:42Z

Use the following:

 System.Text.StringBuilder sb=new System.Text.StringBuilder(); int state=0; for(var i=0;i<Input.Length;i++){ switch(state){ case 0: // beginning if(Input[i]=='('){ state=1; // seen left parenthesis } break; case 2: // seen end parentheses break; // ignore case 1: if(Input[i]==')'){ state=2; // seen right parentheses } else if(Input[i]!='\''){ sb.Append(Input[i]); } break; } } Console.WriteLine(sb.ToString());

Trouble is this might well be quickest (worth checking anyway)
I will reinstate the regular expression if it does turn out to be faster, though I believe it wouldn't make much difference.
As it turns out, the regular expression that was previously here was more than twice as slow, after running each approach 200,000 times.

Vlad Bezden · Accepted Answer · 2011-07-11 22:31:25Z

 var result = new string(Input.ToCharArray(). SkipWhile (i => i != '\''). TakeWhile (i => i != ')').ToArray());

Dunes · Accepted Answer · 2011-07-11 23:02:02Z

Why don't you want to use regular expressions? Regular expressions are heavily optimised and will be much faster than any hand written hack.

This is java (as I run linux and can't run c# as a result), but I hope you get the idea.

input.replace("view(","").replace("'","").replace("\"","").replace(");","");

A million repetitions of the above runs in about 6 seconds on my computer. Whereas, the regular expression below runs in about 2 seconds.

// create java's regex matcher object // matcher is looking for sequences of digits (valid integers) Matcher matcher = Pattern.compile("(\\d+)").matcher(s); StringBuilder builder = new StringBuilder(); // whilst we can find matches append the match plus a comma to a string builder while (matcher.find()) { builder.append(matcher.group()).append(','); } // return the built string less the last trailing comma return builder.substring(0, builder.length()-1);

If you want to find valid decimals as well as integers then use the following pattern instead. Though it runs slightly slower than the original.

"(\\d+(\\.\\d*)?)"

I know you said you didn't want to use regular expressions, but I think you're making a mistake. After the initial learning curve writing a good regex is faster, clearer and cleaner than a hand written alternative, but it will also perform faster than the functional and imperative answers here.

Vlad Bezden · Accepted Answer · 2011-07-11 22:14:39Z

More generic

void Main() { string Input = "view('512', 3, 159);"; var statingPoint = Input.IndexOf('(') + 1; var result = Input.Substring(statingPoint, Input.IndexOf(')') - statingPoint); }

gordy · Accepted Answer · 2011-07-11 22:17:23Z

0

fastest way would be Input = Input.Substring(5, Input.Length - 7)

edited Jul 11, 2011 at 22:17

answered Jul 11, 2011 at 22:10

gordy

9,9713 gold badges37 silver badges49 bronze badges

5 Comments

Femaref Over a year ago

This won't get rid of the quote after 512.

SoftMemes Over a year ago

I assume the question is how to extract part of a string in quotes, not how to extract that specific range in the specific example?

Frédéric Hamidi Over a year ago

@Femaref, or of the one before 512 either.

Guffa Over a year ago

That will cause an ArgumentOutOfRangeException. You can't get characters beyond the end of the string.

gordy Over a year ago

@Guffa: fixed, I forgot the 2nd param is length and not endPos

Collectives™ on Stack Overflow

What's the best way to remove strings?

10 Answers 10

Comments

Comments

Comments

Comments

Comments

3 Comments

Comments

1 Comment

Comments

5 Comments

Hot Network Questions