Valid1: 2
valid2: 3-5
Valid3: 2,4-6
valid4: 2,4,5
valid5: 2-7,8-9
Valid4: 2,5-7,9-13,15,17-20
All the expression on the above should be valid in one regex. the digit in the left side of hyphen should be smaller than right hand side.
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What have you tried so far? No one is going to give you a full answer unless you show what you have tried and where you are stuck.victorantunes– victorantunes2013-10-28 17:06:32 +00:00Commented Oct 28, 2013 at 17:06
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6Regular expressions have no concept of the size of a number. You will need more than a regex to solve this problem.MikeFHay– MikeFHay2013-10-28 17:06:55 +00:00Commented Oct 28, 2013 at 17:06
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for regexp you will need to use the following symbols : + , ( ) \d - you will also need to validate the numbers themselves though because you cannot compare numbers with regexpLogan Murphy– Logan Murphy2013-10-28 17:10:56 +00:00Commented Oct 28, 2013 at 17:10
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i would recommend making your own finite state machineLogan Murphy– Logan Murphy2013-10-28 17:11:44 +00:00Commented Oct 28, 2013 at 17:11
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possible duplicate of Trying to build a regular expression to check patternBrian Rogers– Brian Rogers2013-10-28 17:28:10 +00:00Commented Oct 28, 2013 at 17:28
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1 Answer
First, as @MikeFHay suggested above, regex were not made to check if one digit is bigger than the other (for that you'll have to parse the expression). If we'll ignore that requirement - the rest can be achieved via the following regex:
((\d\,(?=\d))|(\d\-(?=\d))|\d)+
in Java:
"((\\d\\,(?=\\d))|(\\d\\-(?=\\d))|\\d)+"
Explanation:
This regex uses lookahead to validate that each comma or dash is preceded and followed by a digit: (\d\,(?=\d)) so that each "substring" that contains a dash/comma will have to be in the format of: digit,digit or digit-digit.
Of course that a number that doesn't contain commas/dashes is also valid - hence the rightmost side of the or which is simply a \d
Link to online demo
