假设我有一个字符串，“cats cat cat and dogs dogs dogs”。
我会使用什么正则表达式来将该字符串替换为“cats and dogs”。即删除重复项。然而，该表达式只能删除一个接一个的重复项。例如：
“猫猫猫狗狗猫猫狗狗”
会返回：
“猫狗和猫狗”
【问题讨论】：
标签： c# regex duplicates
resultString = Regex.Replace(subjectString, @"\b(\w+)(?:\s+\1\b)+", "$1");
将在一次调用中完成所有替换。
解释：
\b # assert that we are at a word boundary
# (we only want to match whole words)
(\w+) # match one word, capture into backreference #1
(?: # start of non-capturing, repeating group
\s+ # match at least one space
\1 # match the same word as previously captured
\b # as long as we match it completely
)+ # do this at least once
【讨论】：
将(\w+)\s+\1 替换为$1
循环执行此操作，直到找不到更多匹配项。设置global 标志是不够的，因为它不会替换cats cats cats 中的第三个cats
正则表达式中的\1 指的是第一个捕获的组的内容。
试试：
str = "cats cats cats and dogs dogs dogs and cats cats and dogs dogs";
str = Regex.Replace(str, @"(\b\w+\b)\s+(\1(\s+|$))+", "$1 ");
Console.WriteLine(str);
【讨论】：
str = Regex.Replace(str, @"(\w+)\s+\1", "$1");
毫无疑问，可能有一个更小的正则表达式，但这个似乎可以解决问题：
string somestring = "cats cats cats and dogs dogs dogs and cats cats and dogs dogs";
Regex regex = new Regex(@"(\w+)\s(?:\1\s)*(?:\1(\s|$))");
string result = regex.Replace(somestring, "$1$2");
它还考虑了最后不以空格结尾的“狗”。
【讨论】：
cats cats cats and dogs dogs dogs and cats cats and dogs dogs 变为 catsand dogsand catsand dogs。它也匹配太多：Michael Bolton on CD 变为 Michael BoltonCD。对办公空间参考感到抱歉。
$1$2，所以我认为我看到的第一个问题不存在。但迈克尔博尔顿仍然有问题。也许一些催眠会有所帮助（或在\w 之前的单词边界\b）。
试试下面的代码。
using System;
using System.Text.RegularExpressions;
namespace ConsoleApplication1
{
/// <summary>
///
/// A description of the regular expression:
///
/// Match expression but don't capture it. [^|\s+]
/// Select from 2 alternatives
/// Beginning of line or string
/// Whitespace, one or more repetitions
/// [1]: A numbered capture group. [(\w+)(?:\s+|$)]
/// (\w+)(?:\s+|$)
/// [2]: A numbered capture group. [\w+]
/// Alphanumeric, one or more repetitions
/// Match expression but don't capture it. [\s+|$]
/// Select from 2 alternatives
/// Whitespace, one or more repetitions
/// End of line or string
/// [3]: A numbered capture group. [\1|\2], one or more repetitions
/// Select from 2 alternatives
/// Backreference to capture number: 1
/// Backreference to capture number: 2
///
///
/// </summary>
class Class1
{
///
/// Point d'entrée principal de l'application.
///
static void Main(string[] args)
{
Regex regex = new Regex(
"(?:^|\s+)((\w+)(?:\s+|$))(\1|\2)+",
RegexOptions.IgnoreCase
| RegexOptions.Compiled
);
string str = "cats cats cats and dogs dogs dogs and cats cats and dogs dogs";
string regexReplace = " $1";
Console.WriteLine("Before :" + str);
str = regex.Replace(str,regexReplace);
Console.WriteLine("After :" + str);
}
}
}
【讨论】：