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  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Text;
  5. using System.Runtime.InteropServices;
  6. using System.Text.RegularExpressions;
  7. using System.Diagnostics;
  8.  
  9. namespace ca
  10. {
  11.     public class Test
  12.     {
  13.         public static void Main()
  14.         {
  15.             Regex trimmer = new Regex(@"\s\s+", RegexOptions.Compiled);
  16.             Random rng = new Random();
  17.             Stopwatch sw = new Stopwatch();
  18.             const int n = 5;
  19.  
  20.             // random 1mb+ string (it's slow enough...)
  21.             StringBuilder ssb = new StringBuilder(1 * 1024 * 1024);
  22.             for (int i = 0; i < 1 * 1024 * 1024; ++i)
  23.                 if (rng.Next(5) == 0)
  24.                     ssb.Append(new string(' ', rng.Next(20)));
  25.                 else
  26.                     ssb.Append((char)(rng.Next(128 - 32) + 32));
  27.             string s = ssb.ToString();
  28.             StringBuilder tmpbuilder = new StringBuilder(s.Length);
  29. 			// ===================
  30.  
  31.  
  32.  
  33.  
  34.             // ========= regex =========
  35.             sw.Start();
  36.             for (int i = 0; i < n; ++i)
  37.             {
  38.                 string scopy = s;
  39.                 scopy = trimmer.Replace(scopy, " ");
  40.             }
  41.             sw.Stop();
  42.             Console.WriteLine("Regex: " + sw.ElapsedMilliseconds + "ms.");
  43.  
  44.  
  45.             // ========= stringbuilder =========
  46.             sw.Reset(); sw.Start();
  47.             for (int i = 0; i < n; ++i)
  48.             {
  49.                 string scopy = s;
  50.                 bool inspaces = false;
  51.                 tmpbuilder.Length = 0;
  52.  
  53.                 for (int k = 0; k < s.Length; ++k)
  54.                 {
  55.                     char c = scopy[k];
  56.  
  57.                     if (inspaces)
  58.                     {
  59.                         if (c != ' ')
  60.                         {
  61.                             inspaces = false;
  62.                             tmpbuilder.Append(c);
  63.                         }
  64.                     }
  65.                     else if (c == ' ')
  66.                     {
  67.                         inspaces = true;
  68.                         tmpbuilder.Append(' ');
  69.                     }
  70.                     else
  71.                         tmpbuilder.Append(c);
  72.                 }
  73.             }
  74.             sw.Stop();
  75.             Console.WriteLine("Stringbuilder: " + sw.ElapsedMilliseconds + "ms.");
  76.         }
  77.     }
  78. }
Success #stdin #stdout 1.22s 52452KB
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stdin
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Standard input is empty
stdout
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Regex: 1039ms.
Stringbuilder: 68ms.
https://ideone.com/NV6EzU
language:
C# (gmcs 5.20.1)
created:
4 years ago
visibility:
public

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