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?
当前回答
static void Main(string[] args)
{
string str = "";
string reverse = "";
Console.WriteLine("Enter the value to reverse");
str = Console.ReadLine();
int length = 0;
length = str.Length - 1;
while(length >= 0)
{
reverse = reverse + str[length];
length--;
}
Console.Write("Reverse string is {0}", reverse);
Console.ReadKey();
}
其他回答
最简单的方法:
string reversed = new string(text.Reverse().ToArray());
private static string Reverse(string str)
{
string revStr = string.Empty;
for (int i = str.Length - 1; i >= 0; i--)
{
revStr += str[i].ToString();
}
return revStr;
}
比上述方法快
private static string ReverseEx(string str)
{
char[] chrArray = str.ToCharArray();
int len = chrArray.Length - 1;
char rev = 'n';
for (int i = 0; i <= len/2; i++)
{
rev = chrArray[i];
chrArray[i] = chrArray[len - i];
chrArray[len - i] = rev;
}
return new string(chrArray);
}
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
处理所有类型的unicode字符
使用System.Globalization;
public static string ReverseString(this string content) {
var textElementEnumerator = StringInfo.GetTextElementEnumerator(content);
var SbBuilder = new StringBuilder(content.Length);
while (textElementEnumerator.MoveNext()) {
SbBuilder.Insert(0, textElementEnumerator.GetTextElement());
}
return SbBuilder.ToString();
}
必须提交一个递归的例子:
private static string Reverse(string str)
{
if (str.IsNullOrEmpty(str) || str.Length == 1)
return str;
else
return str[str.Length - 1] + Reverse(str.Substring(0, str.Length - 1));
}
