正则表达式:匹配 x 次或 y 次 [英] regular expressions: match x times OR y times

问题描述

假设一个模式连续出现 3 或 6 次，我需要匹配它.我能得到的最接近的是 \d{3,6} 之类的东西，但这并不能完全满足我的需求.

Lets say I need to match a pattern if it appears 3 or 6 times in a row. The closest I can get is something like \d{3,6} but that doesn't quite do what I need.

'123' 应该匹配
'123456' 应该匹配
'1234' 不应该匹配

'123' should match
'123456' should match
'1234' should not match

推荐答案

^(\d{3}|\d{6})$

你必须有某种终止符，否则 \d{3} 将匹配 1234.这就是我把 ^ 和 $ 放在上面的原因.一种替代方法是使用环视:

You have to have some sort of terminator otherwise \d{3} will match 1234. That's why I put ^ and $ above. One alternative is to use lookarounds:

(?<!\d)(\d{3}|\d{6})(?!\d)

确保它前面或后面没有数字(在这种情况下).前瞻和后视零宽度断言中的更多信息.

to make sure it's not preceded by or followed by a digit (in this case). More in Lookahead and Lookbehind Zero-Width Assertions.

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