Question

如果字符串包含的数字小于或等于20且只允许使用数字，我需要正则表达式返回true。

Answer 1

假设您匹配的是以下数字：

整数
在[0,20]

这应该有效：^(([01]?[0-9])|(20))$。

如果你匹配花车，事情就会变得有些麻烦。理想情况下，检查数值范围应始终通过平台的数字运算符完成。

Answer 2

我不知道支持正则表达式的语言。我将假设它使用了PCRE的一些变体。

此处的代码是严格验证字符串仅包含数字。

只有整数，假设非负数，没有前导0：

^(1?\d|20)$

只有整数，假设为非负数，允许任意前导0：

^0*(1?\d|20)$

任何整数，没有前导0：

^(+?(1?\d|20)|-\d+)$

任何整数，允许任意前导0：

^(+?0*(1?\d|20)|-\d+)$

如果数字不是任意大，那么最好使用松散的正则表达式\b[+-]?\d+(\.\d*)?\b捕获数字，然后将其转换为数字并检查它。

Answer 3

这将匹配小于或等于20的整数

(?:\b|-)0*([0-9]|1[0-9]|20)\b

<强>解释

(?:            # Match the regular expression below
                  # Match either the regular expression below (attempting the next alternative only if this one fails)
      \b             # Assert position at a word boundary
   |              # Or match regular expression number 2 below (the entire group fails if this one fails to match)
      -              # Match the character “-” literally
)
0              # Match the character “0” literally
   *              # Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
(              # Match the regular expression below and capture its match into backreference number 1
                  # Match either the regular expression below (attempting the next alternative only if this one fails)
      [0-9]          # Match a single character in the range between “0” and “9”
   |              # Or match regular expression number 2 below (attempting the next alternative only if this one fails)
      1              # Match the character “1” literally
      [0-9]          # Match a single character in the range between “0” and “9”
   |              # Or match regular expression number 3 below (the entire group fails if this one fails to match)
      20             # Match the characters “20” literally
)
\b             # Assert position at a word boundary

访问here以了解未来的问题。

Answer 4

(\b[0-9]\b|\b1[0-9]\b|\b20\b)为我工作

只有整数，假设非负数，没有前导0

我曾经发现小于20的百分比，所以它最终成为：

(\b[0-9]%|\b1[0-9]%|\b20%)

包含小于或等于20的数字的正则表达式

4 个答案: