CODEWITHSUNDEEP
phpregex
Julien M.
Julien M.

Reputation: 71

PHP Regex: find all consecutive number sequences in a string?

Not sure if regular expressions are the right approach for this, but here is what I am looking to achieve... within a string composed of sorted digits such as 23412167894125123 I would like to extract all sequences of at least 3 consecutive digits:

Can this be done with regex? Otherwise what could be a sensible approach?

Upvotes: 1

Views: 875

Answers (3)

manjeet
manjeet

Reputation: 1517

If the regex looks too complex, this function uses a simple for loop

function findSeq($string) {

    $seq_started = false;

    $seq = '';

    $list = [];

    for ($i = 1; $i < strlen($string) + 1; $i++) {

        @$curr = $string[$i];
        $prev = $string[$i - 1];
        @$next = $string[$i + 1];

        if ($prev + 1 == $curr) {

            if ($seq_started === false) {

                $seq .= "$prev$curr";

            } else {

                $seq .= $curr;
            }

            $seq_started = true;

            continue;

        }

        if ($seq_started === true) {

            if (strlen($seq) > 2) {

                $list[] = $seq;

            }

            $seq = '';

            $seq_started = false;

        }

    }

    return $list;

}

print_r(findSeq('2341216789412501231456789'));

Output

Array
(
    [0] => 234
    [1] => 6789
    [2] => 0123
    [3] => 456789
)

Upvotes: 1

Croises
Croises

Reputation: 18671

With RegEx, you can use:

(123(?:4(?:5(?:6(?:7(?:89?)?)?)?)?)?|234(?:5(?:6(?:7(?:89?)?)?)?)?|345(?:6(?:7(?:89?)?)?)?|456(?:7(?:89?)?)?|567(?:89?)?|6789?|789)

Try here: https://regex101.com/r/Ap8C2D/1

If you test also with 012…:

(012(?:3(?:4(?:5(?:6(?:7(?:89?)?)?)?)?)?)?|123(?:4(?:5(?:6(?:7(?:89?)?)?)?)?)?|234(?:5(?:6(?:7(?:89?)?)?)?)?|345(?:6(?:7(?:89?)?)?)?|456(?:7(?:89?)?)?|567(?:89?)?|6789?|789)

Test: https://regex101.com/r/zm6I9x/1

Upvotes: 4

David
David

Reputation: 6131

You could use RegEx, but to be honest this would be much simpler to implement a loop and check if the numbers are sequential inside of the loop. Take a look at this example:

$literal = '23412167894125123';

for ($c = 0; $c < strlen($literal) - 2; $c++) {
    if(intval($literal[$c]) + 1 == intval($literal[$c + 1]) &&
       intval($literal[$c]) + 2 == intval($literal[$c + 2])) {
        echo $literal[$c], $literal[$c + 1], $literal[$c + 2], '<br />';
    }
}

Fiddle: Live Demo

Upvotes: 2

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