如何擺脫正則表達式中的重復

Question

假設我有一根繩子，“貓貓貓狗狗狗”。

我將使用什么正則表達式來替換“貓與狗”的字符串。 即刪除重復項。 但是，表達式只能刪除彼此之后的重復項。 例如：

“貓貓貓狗狗狗貓貓貓狗”

會回來：

“貓與狗，貓與狗”

Answer 1

resultString = Regex.Replace(subjectString, @"\b(\w+)(?:\s+\1\b)+", "$1");

將在一個電話中完成所有替換。

說明：

\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

Answer 2

用$1替換(\\w+)\\s+\\1 $1

在循環中執行此操作，直到找不到更多匹配項。 設置global標志是不夠的，因為它不會取代cats中的第三cats cats cats

正則表達式中的\\1指的是第一個捕獲組的內容。

嘗試：

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);

Answer 3

毫無疑問，有一個較小的正則表達式可能，但這個似乎可以做到這一點：

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");

它還考慮到最后一個沒有空格結尾的“狗”。

Answer 4

請嘗試以下代碼。

---

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);
    }
}

}