我刚刚在c# 2.0中写了一个字符串反向函数(即LINQ不可用),然后想到了这个:
public string Reverse(string text)
{
char[] cArray = text.ToCharArray();
string reverse = String.Empty;
for (int i = cArray.Length - 1; i > -1; i--)
{
reverse += cArray[i];
}
return reverse;
}
就我个人而言,我并不喜欢这个功能,我相信有更好的方法来实现它。是吗?
抱歉写了这么长时间,但这可能会很有趣
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
public static string ReverseUsingArrayClass(string text)
{
char[] chars = text.ToCharArray();
Array.Reverse(chars);
return new string(chars);
}
public static string ReverseUsingCharacterBuffer(string text)
{
char[] charArray = new char[text.Length];
int inputStrLength = text.Length - 1;
for (int idx = 0; idx <= inputStrLength; idx++)
{
charArray[idx] = text[inputStrLength - idx];
}
return new string(charArray);
}
public static string ReverseUsingStringBuilder(string text)
{
if (string.IsNullOrEmpty(text))
{
return text;
}
StringBuilder builder = new StringBuilder(text.Length);
for (int i = text.Length - 1; i >= 0; i--)
{
builder.Append(text[i]);
}
return builder.ToString();
}
private static string ReverseUsingStack(string input)
{
Stack<char> resultStack = new Stack<char>();
foreach (char c in input)
{
resultStack.Push(c);
}
StringBuilder sb = new StringBuilder();
while (resultStack.Count > 0)
{
sb.Append(resultStack.Pop());
}
return sb.ToString();
}
public static string ReverseUsingXOR(string text)
{
char[] charArray = text.ToCharArray();
int length = text.Length - 1;
for (int i = 0; i < length; i++, length--)
{
charArray[i] ^= charArray[length];
charArray[length] ^= charArray[i];
charArray[i] ^= charArray[length];
}
return new string(charArray);
}
static void Main(string[] args)
{
string testString = string.Join(";", new string[] {
new string('a', 100),
new string('b', 101),
new string('c', 102),
new string('d', 103),
});
int cycleCount = 100000;
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
for (int i = 0; i < cycleCount; i++)
{
ReverseUsingCharacterBuffer(testString);
}
stopwatch.Stop();
Console.WriteLine("ReverseUsingCharacterBuffer: " + stopwatch.ElapsedMilliseconds + "ms");
stopwatch.Reset();
stopwatch.Start();
for (int i = 0; i < cycleCount; i++)
{
ReverseUsingArrayClass(testString);
}
stopwatch.Stop();
Console.WriteLine("ReverseUsingArrayClass: " + stopwatch.ElapsedMilliseconds + "ms");
stopwatch.Reset();
stopwatch.Start();
for (int i = 0; i < cycleCount; i++)
{
ReverseUsingStringBuilder(testString);
}
stopwatch.Stop();
Console.WriteLine("ReverseUsingStringBuilder: " + stopwatch.ElapsedMilliseconds + "ms");
stopwatch.Reset();
stopwatch.Start();
for (int i = 0; i < cycleCount; i++)
{
ReverseUsingStack(testString);
}
stopwatch.Stop();
Console.WriteLine("ReverseUsingStack: " + stopwatch.ElapsedMilliseconds + "ms");
stopwatch.Reset();
stopwatch.Start();
for (int i = 0; i < cycleCount; i++)
{
ReverseUsingXOR(testString);
}
stopwatch.Stop();
Console.WriteLine("ReverseUsingXOR: " + stopwatch.ElapsedMilliseconds + "ms");
}
}
}
结果:
ReverseUsingCharacterBuffer: 346毫秒
ReverseUsingArrayClass: 87毫秒
ReverseUsingStringBuilder: 824毫秒
ReverseUsingStack: 2086毫秒
ReverseUsingXOR: 319毫秒
我从Microsoft.VisualBasic.Strings中做了一个c#移植。我不知道他们为什么把这么有用的函数(从VB)保存在系统之外。框架中的字符串,但仍然在Microsoft.VisualBasic下。同样的场景用于财务函数(例如microsoft . visualbasic . finance . pmt())。
public static string StrReverse(this string expression)
{
if ((expression == null))
return "";
int srcIndex;
var length = expression.Length;
if (length == 0)
return "";
//CONSIDER: Get System.String to add a surrogate aware Reverse method
//Detect if there are any graphemes that need special handling
for (srcIndex = 0; srcIndex <= length - 1; srcIndex++)
{
var ch = expression[srcIndex];
var uc = char.GetUnicodeCategory(ch);
if (uc == UnicodeCategory.Surrogate || uc == UnicodeCategory.NonSpacingMark || uc == UnicodeCategory.SpacingCombiningMark || uc == UnicodeCategory.EnclosingMark)
{
//Need to use special handling
return InternalStrReverse(expression, srcIndex, length);
}
}
var chars = expression.ToCharArray();
Array.Reverse(chars);
return new string(chars);
}
///<remarks>This routine handles reversing Strings containing graphemes
/// GRAPHEME: a text element that is displayed as a single character</remarks>
private static string InternalStrReverse(string expression, int srcIndex, int length)
{
//This code can only be hit one time
var sb = new StringBuilder(length) { Length = length };
var textEnum = StringInfo.GetTextElementEnumerator(expression, srcIndex);
//Init enumerator position
if (!textEnum.MoveNext())
{
return "";
}
var lastSrcIndex = 0;
var destIndex = length - 1;
//Copy up the first surrogate found
while (lastSrcIndex < srcIndex)
{
sb[destIndex] = expression[lastSrcIndex];
destIndex -= 1;
lastSrcIndex += 1;
}
//Now iterate through the text elements and copy them to the reversed string
var nextSrcIndex = textEnum.ElementIndex;
while (destIndex >= 0)
{
srcIndex = nextSrcIndex;
//Move to next element
nextSrcIndex = (textEnum.MoveNext()) ? textEnum.ElementIndex : length;
lastSrcIndex = nextSrcIndex - 1;
while (lastSrcIndex >= srcIndex)
{
sb[destIndex] = expression[lastSrcIndex];
destIndex -= 1;
lastSrcIndex -= 1;
}
}
return sb.ToString();
}