TLCube.com

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace Testi1
{
    class Program
    {
        static void Main(string[] args)
        {
            int loopCount = 1000000;
            long startTime, endTime;
            double nanoseconds;
 
            startTime = DateTime.Now.Ticks * 100;
            for (int x = 0; x < loopCount; x++)
            {
                ExtractNumbers1("Its is only 4 numbers but must be 1337");
            }
            endTime = DateTime.Now.Ticks * 100;
            nanoseconds = ((double)(endTime - startTime)) / ((double)loopCount);
            Console.WriteLine(nanoseconds.ToString("F") + " ns per operation");
 
            startTime = DateTime.Now.Ticks * 100;
            for (int x = 0; x < loopCount; x++)
            {
                ExtractNumbers2("Its is only 4 numbers but must be 1337");
            }
            endTime = DateTime.Now.Ticks * 100;
            nanoseconds = ((double)(endTime - startTime)) / ((double)loopCount);
            Console.WriteLine(nanoseconds.ToString("F") + " ns per operation");
 
            startTime = DateTime.Now.Ticks * 100;
            for (int x = 0; x < loopCount; x++)
            {
                ExtractNumbers3("Its is only 4 numbers but must be 1337");
            }
            endTime = DateTime.Now.Ticks * 100;
            nanoseconds = ((double)(endTime - startTime)) / ((double)loopCount);
            Console.WriteLine(nanoseconds.ToString("F") + " ns per operation");
 
            Console.Read();
        }
 
        static string ExtractNumbers1(string expr)
        {
            return string.Join(null, System.Text.RegularExpressions.Regex.Split(expr, "[^\\d]"));
        }
 
        static string ExtractNumbers2(string expr)
        {
            StringBuilder sb = new StringBuilder(expr.Length);
 
            foreach (char ch in expr)
            {
                if (Char.IsDigit(ch))
                    sb.Append(ch);
            }
 
            return sb.ToString();
        }
 
        static string ExtractNumbers3(string expr)
        {
            char[] nums = new char[expr.Length];
            int pos = 0;
 
            foreach (char ch in expr)
            {
                if( Char.IsDigit( ch ))
                    nums[pos++] = ch;
            }
 
            return new string ( nums, 0, pos );
        }
    }
}