由特定字符组成的单词的正则表达式 [英] Regex for words formed with specific characters

问题描述

我正在寻找一个正则表达式来匹配由特定字符组成的单词而不重复任何字符:例如，对于 a b c 和 d，如何指定一个正则表达式来匹配这些字符串:

I am looking for a regex to match words formed with specific characters without repeating any character: Example, for a b c and d, how to specify a regex to match those strings:

bdca(匹配)亚行(匹配)abcg(失败)aab(失败)我试过 ^[abcd]{1,4}$ 但它接受重复的字符(最后一个例子).

bdca (match) adb (match) abcg (fail) aab (fail) I tried with ^[abcd]{1,4}$ but it accepts repeated characters (last example).

请帮忙?

推荐答案

你可以使用这个基于负前瞻的正则表达式:

You can use this regex based on negative lookahead:

^(?:([abcd])(?!.*\1)){1,4}$

正则表达式演示

分手:

^            Line start
(?:          Start non-capturing group
  ([abcd])   Match a or b or c or d and group it 
  (?!.*\1)   Negative lookahead to fail the match if same grouped char is ahead
){1,4}       1 to 4 occurrences of non-capturing group
$            Line end

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