regex - 生成正则表达式

Question

任何人都可以帮我创建一个可以检查数字是否有 2 和 4 个重复数字的正则表达式，例如如何检查这个 no 5555122。

我想通过正则表达式知道有第四个双倍的重复。

Answer 1

您可以使用反向引用

(\d)\1{3}

这将检查 4 位数字的重复

Answer 2

尝试这个

(\d)(?:\1{3}|\1)

解释

"
(           # Match the regular expression below and capture its match into backreference number 1
   \\d          # Match a single digit 0..9
)
(?:         # Match the regular expression below
               # Match either the regular expression below (attempting the next alternative only if this one fails)
      \\1          # Match the same text as most recently matched by capturing group number 1
         {3}         # Exactly 3 times
   |           # Or match regular expression number 2 below (the entire group fails if this one fails to match)
      \\1          # Match the same text as most recently matched by capturing group number 1
)
"

编辑

里面的图案(?:\1{3}|\1)，需要多加注意。如果是这样(?:\1|\1{3})，它将与预期不符。因为，The Regex-Directed Engine Always Returns the Leftmost Match。