CODEWITHSUNDEEP
c#regex
Marcin
Marcin

Reputation: 427

Regex - matching patterns without brackets

for example I have this string :

ABCDFFFE[_]XXX[_]O0[_]%[TT]__

What I want do achive is, match/change all _ into ?, and % into *, but NOT ! those inside brackets. The last thing is to remove bracket, but I could make it by string replace.

So my output after regex should be like this :

ABCDFFFE[_]XXX[_]O0[_]*[TT]??

and after string replace (or maybe it could be done with regex too) 

ABCDFFFE_XXX_O0_%TT__

Thanks in advance

Upvotes: 0

Views: 230

Answers (2)

Casimir et Hippolyte
Casimir et Hippolyte

Reputation: 89557

If you already know that each opening bracket has a closing bracket (brackets are balanced), you can test if a closing bracket doesn't follow with a negative lookahead:

var result = Regex.Replace(s, @"[_%](?![^\]\[]*\])", m => m.Value == "_" ? "?" : "*");

Upvotes: 1

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626806

Since the [...] texts cannot be nested, you can use the following regex:

(\[[^][]*])|[_%]

See the regex demo

It will capture [...] subtexts into Group 1 (so that we can restore them in the replacement result later) and just matches _ or %.

Use it in the code like this:

var s = "ABCDFFFE[_]XXX[_]O0[_]%[TT]__";
var result = Regex.Replace(s, @"(\[[^][]*])|[_%]", m =>
            m.Groups[1].Success ? m.Groups[1].Value : m.Value == "_" ? "?" : "*");

The m match evaluator block checks if the Group 1 was matched, and if yes, we insert m.Groups[1].Value. If not, we check the m.Value: if it is _, replace with ? (see m.Value == "_" ? "?"), if not - replace with *.

UPDATE

To obtain Result #2, the string without [ and ], you can use

var result = Regex.Replace(te, @"(\[([^][]*)])|[_%]", m =>
            m.Groups[1].Success ? m.Groups[2].Value : m.Value == "_" ? "?" : "*");

The pattern (\[([^][]*)])|[_%] will capture the whole [...] into Group 1 and the contents inside it into Group 2. If Group 1 matches, Group 2 is initialized and we can refer to it with m.Groups[2].Value.

See IDEONE demos for both solutions

Upvotes: 3

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