preg_match for repeating numeric patterms

[CorvusPrime]

I am looking for a preg_match expression that will find recurring numeric patterns in a space delimited list of 1-2 digit numbers.

 

ex: 12 5 6 7 8 7 7 8 7 3 21  and regex should find 787 as the first repeating pattern.

 

New to regex and trying to get my head around this so I can do it lucidly in the future.

 

 

BTW: I have tried the following:

 

/[0-9]{1,2} [0-9]{1,2} [0-9]{1,2}/\1+

 

And what I get is an error about unknown modifier in reference to the final \1+

[.josh]

what do you consider a repeated pattern?

 

1 2 3 1 2 4

 

is "1 2" considered a repeated pattern?

[CorvusPrime]

Thanks for jumping in.  The answer is three as in "1 2 3" is a pattern.

[.josh]

now wait a minute, that's a different pattern.. "1 2 3" is *a* pattern in that it is sequence of numbers with the same incremented value, but "1 2 3" is not the same pattern definition as "7 8 7" in your example.  In my example, "1 2 3" is not  repeated...

[CorvusPrime]

I misread your example. Specifically we are looking for repeating patterns in a string that consists of numbers of up tp two digits and spaces.

 

A second example would be a string such as:

 

1 12 3 4 12 3 4 5 6 2 3 6 2 3 4 1

 

In the above string the number sequence "12 3 4" is repeated once and is the first repeating pattern. That is what I am trying to return with the regex.  The first pattern of three space delimited numbers that are repeated.

[.josh]

okay so back to my original question, are TWO numbers considered a repeated pattern, or does it have to be a minimum of 3?

[CorvusPrime]

Not two. A sequence of three repeating numbers. ex: 12 3 4

[.josh]

3 or more or exactly 3?

 

I hope you are seeing a theme to my questions here...be more specific in what you want

[CorvusPrime]

Agreed. Let's do three or more. And sorry...dealing with VERY vague reqs on my end.

[.josh]

Okay, one more question...do the numbers have to be next to each other?

 

eg:

 

1 2 3 1 2 3

 

vs.

 

1 2 3 4 1 2 3

 

 

 

 

[CorvusPrime]

Adjacency is not a requirement. And we only need to return the first match found.

 

[.josh]

$string = "12 5 6 12 5 7 8 7 5 7 8 7 3 21 12 5 6";
preg_match('~((\d+\s?){3,}).*\1~',$string,$matches);
$number = $matches[1];

[CorvusPrime]

Thanks so much!!

 

Trying it against this string:

 

2 0 7 1 1 7 1 1 6 8 7

 

and it is returning no matches on 7 1 1.

[.josh]

hmm...then you must have more to the string than you've mentioned, or else you have some other code not working properly.

 

$string = "2 0 7 1 1 7 1 1 6 8 7";
preg_match('~((\d+\s?){3,}).*\1~',$string,$matches);
$number = $matches[1];

echo $number;

 

that echo's "7 1 1"

[CorvusPrime]

Had an offset param ;o) Fixed now. Thanks for this! I am going to study this and get the regex thing "on board".

[.josh]

oooh actually I found a bug in my pattern...apparently it will match partial numbers.  For example:

 

112 5 6 12 5 7 8 7 5 7 8 7 3 21 12 5 60

 

Pattern will match "12 5 6" that's no bueno...

 

Here is an updated pattern that makes use of lookarounds to make sure it matches whole numbers...

 

$string = "2 0 7 1 1 7 1 1 6 8 7";
preg_match('~(((?<!\d)\d+\s?){3,}).*(?<!\d)\1(?!\d)~',$string,$matches);
$number = $matches[1];

[CorvusPrime]

Gotcha. Interesting! I tried a few patterns on my own and definitely appreciate the one you sent over. By far the simplest implementation. Part of the madness that comes with regex noobs...over-complication-itis