如何获取以连字符开头的匹配字符串和使用正则表达式的字符

Question

I have two strings

100-2000

and

100-X200-2012

I try to write regex that match both strings like below by saying that if the second hyphen start with X ignore it

[0-9]+-[a-zA-Z0-9 \-X]+-[0-9]

but it fail to match it, I am not sure how to match it with my criteria ?

Answer 1

Since you haven't specified a tool, I'll go with the .NET regex flavor (my personal favorite):

\d+(-[ \w-[_X]][ \w-[_]]+)?-\d+

\\d is the same as [0-9]

In .NET, you can use character class subtraction to remove particular elements from a characters class. In this case, I've included a space and a \\w (which is the same as [0-9a-zA-Z_]) within the character class and then subtracted the underscore and uppercase X.

Another option is to use negative lookahead:

\d+(-(?!X)[ 0-9a-zA-Z]+)?-\d+

I like this even better, but not all flavors of regex support it.

Answer 2

你的意思是：

[0-9]+-[^X][a-zA-Z0-9 \-]*-[0-9]+

Answer 3

可能是这样的

(\d*)(-X\d*|)-(\d{4})