Here's a few implementations to extract a integer found at beginning of a string.
See my post on the fastest method to extract the 1st found integer anywhere in a string.
The comparisons below are predicated on first extracting the lead digits found in a string ( sign integer allowed), and then converting the string of numbers into an integer.
This is not Unicode compliant, but works for English speaking populations using ASCII numerals 0-9.
Code in case above service perishes.
See my post on the fastest method to extract the 1st found integer anywhere in a string.
The comparisons below are predicated on first extracting the lead digits found in a string ( sign integer allowed), and then converting the string of numbers into an integer.
This is not Unicode compliant, but works for English speaking populations using ASCII numerals 0-9.
Code in case above service perishes.
using System; using System.Diagnostics; using System.Text; using System.Text.RegularExpressions; public static class StringExtensions { public static string GetAllIntRegex(this string numint) { return Regex.Replace(numint, "[^0-9]", ""); } public static string GetLeadIntFast(this string numint) { bool minus = false; //we pass in absolute number if (numint.IndexOf('-') == 0) { minus = true; numint = numint.Replace("-", ""); //we expect this to be in first place, not bullet proof but GE } else if (numint.IndexOf('+') == 0) numint = numint.Replace("+", ""); char[] n = numint.ToCharArray(); StringBuilder sb = new StringBuilder(); for (int i = 0; i < n.Length; i++) { if (!char.IsDigit(n[i])) break; sb.Append(n[i]); } if (minus) return string.Concat("-", sb.ToString()); return sb.ToString(); } public static string GetLeadIntFaster(this string numint) { bool minus = false; //we pass in absolute number if (numint.IndexOf('-') == 0) { minus = true; numint = numint.Replace("-", ""); //we expect this to be in first place } else if (numint.IndexOf('+') == 0) numint = numint.Replace("+", ""); char[] n = numint.ToCharArray(); int exit = 0; for (int i = 0; i < n.Length; i++) { if (!char.IsDigit(n[i])) { exit = i; break; } } Array.Resize(ref n, exit); if (minus) return string.Concat("-", new string(n)); return new string(n); }
public static string GetLeadIntFastest(this string numint)
{
bool minus = false; //we pass in absolute number
if (numint.IndexOf('-') == 0)
{
minus = true;
numint = numint.Substring(1); //we expect this to be in first place
}
else if (numint.IndexOf('+') == 0)
numint = numint.Substring(1);
char[] n = numint.ToCharArray(); //faster indexing that string indexing
int exit = 0;
for (int i = 0; i < n.Length; i++)
{
if (!char.IsDigit(n[i]))
{
exit = i;
break;
}
}
Array.Resize(ref n, exit);
if (minus)
return string.Concat("-", new string(n));
return new string(n);
}
public static int TryParser(this string numint)
{
int y = 0;
//This is a fair comparison, we must get digits only
Int32.TryParse(numint.GetLeadIntFast(), out y); //this alone is fast at 502 ticks
return y;
}
public static int TryParserFaster(this string numint)
{
int y = 0;
//This is a fair comparison, we must get digits only
Int32.TryParse(numint.GetLeadIntFaster(), out y); //this alone is fast at 502 ticks
return y;
}
public static int TryParserFastest(this string numint)
{
int y = 0;
//This is a fair comparison, we must get digits only
Int32.TryParse(numint.GetLeadIntFastest(), out y); //this alone is fast at 502 ticks
return y;
}
public static int TryParserRegex(this string numint)
{
int y = 0;
//This is a fair comparison, we must get digits only
Int32.TryParse(numint.GetAllIntRegex(), out y); //this alone is fast at 502 ticks
return y;
}
/// <summary>
/// Fastest wat to convert a numeric string into an int
/// </summary>
/// <param name="numint">must be numbers and signs only</param>
/// <returns></returns>
public static int StartsWithInt(this string numint)
{
bool minus = false; //we pass in absolute number
if (numint.IndexOf('-') == 0)
{
minus = true;
numint = numint.Replace("-", ""); //we expect this to be in first place, not bullet proof but GE
}
else if (numint.IndexOf('+') == 0)
numint = numint.Replace("+", "");
int total = 0; //must be zero
for (int i = 0; i < numint.Length; i++)
{
if (numint[i] >= '0' && numint[i] <= '9') //get lead number only
{
if (total * 10 + (numint[i] - '0') < 0) //we get into negative, if over int.MaxValue
return int.MaxValue; //return what you want or throw error
total = total * 10 + (numint[i] - '0');
}
else
break;
//return int.MinValue;
}
if (minus) total *= -1;
return total;
}
/// <summary>
/// Fastest way to convert lead digits in a string into an int
/// </summary>
/// <param name="intStr">must be numbers and signs only</param>
/// <returns></returns>
public static int StartsWithIntFaster(this string intStr)
{
bool minus = false; //we pass in absolute number
if (intStr.IndexOf('-') == 0)
{
minus = true;
intStr = intStr.Replace("-", ""); //we expect this to be in first place, not bullet proof but GE
}
else if (intStr.IndexOf('+') == 0)
intStr = intStr.Replace("+", "");
int sum = 0; //must be zero
char[] n = intStr.ToCharArray();
for (int i = 0; i < n.Length; i++)
{
if (n[i] >= 48 && n[i] <= 57) //'0'=48 and '9'=57 get lead number only
{
int z = sum * 10 + (n[i] - 48);
if (z < 0) //we get into negative, if over int.MaxValue
return int.MaxValue; //return what you want or throw error
sum = z;
}
else
break; //returns lead digits
//or return int.MinValue;
}
if (minus) sum *= -1;
return sum;
}
//WINNER
/// <summary>
/// Fastest way to convert lead digits in a string into an int
/// </summary>
/// <param name="intStr">must be numbers and signs only</param>
/// <returns></returns>
public static int StartsWithIntFastest(this string intStr)
{
bool minus = false; //we need to pass in absolute number
if (intStr.IndexOf('-') == 0)
{
minus = true;
intStr = intStr.Substring(1); //we expect this to be in first place, not bullet proof but GE
}
else if (intStr.IndexOf('+') == 0)
intStr = intStr.Substring(1);
int sum = 0; //must be zer0
char[] n = intStr.ToCharArray();
for (int i = 0; i < n.Length; i++)
{
if (n[i] >= 48 && n[i] <= 57) //'0'=48 and '9'=57 get lead number only
{
int z = sum * 10 + (n[i] - 48);
if (z < 0) //we get into negative, if over int.MaxValue
return int.MaxValue; //return what you want or throw error
sum = z;
}
else
break; //returns lead digits
//return int.MinValue; //or throw error
}
if (minus) sum *= -1;
return sum;
}
}
public class Program
{
public static void Main()
{
Stopwatch sw = new Stopwatch();
sw.Start();
Console.WriteLine("12451a 1".StartsWithInt());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("12452a 2".StartsWithIntFaster());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("Winner");
Console.WriteLine("12453a 3".StartsWithIntFastest());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("12454a 4".TryParser());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("12455a 5".TryParserFaster());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("12456a 6".TryParserFastest());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
sw.Reset();
sw.Start();
Console.WriteLine("This grabs all numbers and NOT JUST LEAD digits!");
Console.WriteLine("12457a 7".TryParserRegex());
sw.Stop();
Console.WriteLine(sw.ElapsedTicks.ToString() + " ticks");
Console.WriteLine("0".StartsWithIntFastest());
Console.WriteLine("10".StartsWithIntFastest());
Console.WriteLine("-12345".StartsWithIntFastest());
Console.WriteLine("1234".StartsWithIntFastest());
Console.WriteLine("123".StartsWithIntFastest());
Console.WriteLine("+12346".StartsWithIntFastest());
Console.WriteLine("-1234".StartsWithIntFastest());
Console.WriteLine("21474813649".StartsWithIntFastest());
}
}
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