Regular expression Match for numeric pattern

Question

I am working on parsing the user provided input for a number which belongs to a specified pattern such as 199-234

where the

first component is 1
second component is 99
third component is 234

The user would provide just the first few digits or the entire string. I intend to parse each of the components out. The reg-ex that I have come up with is -

Regex regex = new Regex(@"(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3})");
var groups = regex.Match(input);

If I provide the input 199 , the reg-ex pattern breaks them into 3 groups instead of the expected 2. Actual result is

first component is 1
second component is 9
third component is 9

How do I ensure that the inputs get correctly matched in this case?

Jeff Swensen · Accepted Answer · 2011-05-10 00:59:50Z

3

Try the non-greedy version of the third group: \d{0,3}?

Regex regex = new Regex(@"(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3}?)");
var groups = regex.Match(input);

It also might help (for clarity's sake) to bind the beginning and end of the strings (^ and $)

new Regex(@"^(?<first>\d)(?<second>\d{0,2})-?(?<third>\d{0,3}?)$");

edited May 10, 2011 at 0:59

answered May 10, 2011 at 0:29

Jeff Swensen

3,57331 silver badges52 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Reubene · Accepted Answer · 2011-05-10 00:29:49Z

0

Because your expression requires a third element it cannot match 199 as only two groups because it needs three groups for a match.

Also you are allowsing matches of zero length for your second and third groups.

Try requireing exactly two characters for the second group or making the third group optional.

answered May 10, 2011 at 0:29

Reubene

1462 bronze badges

Comments

stema · Accepted Answer · 2011-05-10 06:35:35Z

0

Make the complete last part optional and not only the -

@"(?<first>\d)(?<second>\d{0,2})(?:-(?<third>\d{0,3}))?"

I put the complete last part starting with the - into an optional non-capturing ((?:)) group (?:-(?<third>\d{0,3}))?. So it will search only for the third group if there is a -.

answered May 10, 2011 at 6:35

stema

93.5k20 gold badges110 silver badges138 bronze badges

1 Comment

user673872 Over a year ago

Thanks stema. Let me give this a go as well.

Collectives™ on Stack Overflow

Regular expression Match for numeric pattern

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related