Fastest way to remove first char in a String
Say we have the following string
string data= "/temp string";
If we want to remove the first character /
we can do by a lot of ways such as :
data.Remove(0,1);
data.TrimStart('/');
data.Substring(1);
But, really I don't know which one has the best algorithm and doing that faster..
Is there a one that is the best or all are the same ?
The second option really isn't the same as the others - if the string is "///foo" it will become "foo" instead of "//foo".
The first option needs a bit more work to understand than the third - I would view the Substring
option as the most common and readable.
(Obviously each of them as an individual statement won't do anything useful - you'll need to assign the result to a variable, possibly data
itself.)
I wouldn't take performance into consideration here unless it was actually becoming a problem for you - in which case the only way you'd know would be to have test cases, and then it's easy to just run those test cases for each option and compare the results. I'd expect Substring
to probably be the fastest here, simply because Substring
always ends up creating a string from a single chunk of the original input, whereas Remove
has to at least potentially glue together a start chunk and an end chunk.
I know this is hyper-optimization land, but it seemed like a good excuse to kick the wheels of BenchmarkDotNet
. The result of this test (on .NET Core even) is that Substring
is ever so slightly faster than Remove
, in this sample test: 19.37ns vs 22.52ns for Remove
. So some ~16% faster.
using System;
using BenchmarkDotNet.Attributes;
namespace BenchmarkFun
{
public class StringSubstringVsRemove
{
public readonly string SampleString = " My name is Daffy Duck.";
[Benchmark]
public string StringSubstring() => SampleString.Substring(1);
[Benchmark]
public string StringRemove() => SampleString.Remove(0, 1);
public void AssertTestIsValid()
{
string subsRes = StringSubstring();
string remvRes = StringRemove();
if (subsRes == null
|| subsRes.Length != SampleString.Length - 1
|| subsRes != remvRes) {
throw new Exception("INVALID TEST!");
}
}
}
class Program
{
static void Main()
{
// let's make sure test results are really equal / valid
new StringSubstringVsRemove().AssertTestIsValid();
var summary = BenchmarkRunner.Run<StringSubstringVsRemove>();
}
}
}
Results:
BenchmarkDotNet=v0.11.4, OS=Windows 10.0.17763.253 (1809/October2018Update/Redstone5)
Intel Core i7-6700HQ CPU 2.60GHz (Skylake), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=3.0.100-preview-010184
[Host] : .NET Core 3.0.0-preview-27324-5 (CoreCLR 4.6.27322.0, CoreFX 4.7.19.7311), 64bit RyuJIT
DefaultJob : .NET Core 3.0.0-preview-27324-5 (CoreCLR 4.6.27322.0, CoreFX 4.7.19.7311), 64bit RyuJIT
| Method | Mean | Error | StdDev |
|---------------- |---------:|----------:|----------:|
| StringSubstring | 19.37 ns | 0.3940 ns | 0.3493 ns |
| StringRemove | 22.52 ns | 0.4062 ns | 0.3601 ns |