php vertical regular expression search

问题

I've a string describing a matrix of n x m elements like this one:

§inputmap = "
~~~~~~~~~~~~~~~~~~~~B~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~BBB........BBB~~~~~~~~~~~~~
~~~~~~~~~~BB...............FBB~~~~~~~~~~
~~~~~~~~BB....................BB~~~~~~~~
~~~~~~BB.....F..................BB~~~~~~
~~~~~BB.....................F.....B~~~~~
~~~~B..............................B~~~~
~~~B........F.......................B~~~
~~BB.........F......................BB~~
~~B................F.................BB~
~BF....F....F........................FB~
~B.....................................B
B.....................................FB
B........F......F......................B
B...........................F..........B
B......................................B
B......................................B
B.......F.......................F......B
B......FFF.............................B
B.......F.............................FB
~B..................F.................FB
~BF...........................F.......B~
~~B...F...........F..........FFFFF.F.BB~
~~BB..................F..F....F.....BB~~
~~~B.......................FF.FF....B~~~
~~~~B..............................B~~~~
~~~~~BB...........................B~~~~~
~~~~~~BB........................BB~~~~~~
~~~~~~~~BB..........F..........B~~~~~~~~
~~~~~~~~~~BB................BB~~~~~~~~~~
~~~~~~~~~~~~~BBB.......F.BBB~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~BBBBBB~~~~~~~~~~~~~~~~~
";
$inputmap = trim($inputmap);

I need to build a regular expression (or something else) to search the string:

$search = "
*F*
FFF
*F*
";
$search = trim($search);

on the whole grid. On other hands I need to find a pattern of 5 distinct letter "F" (3 vertically and 3 horizzontally) getting back the rows/columns position of the pattern(s) found on the map.

Considering that the input matrix can be different (5x5 or 10x10 or 20x25 or ...), is there a way to solve my problem with php and regular expressions?

回答1:

You can do something like this (without regular expressions) :

$map = explode("\n", $inputmap);

for ($vcount = 0; $vcount < sizeof($map); ++$vcount) {  // Loop through the map vertically
    for ($hcount = 0; $hcount < strlen($map[$vcount]); ++$hcount) { // Loop through each character of each line
        if ($map[$vcount][$hcount] == "F") {
            if ($map[$vcount + 1][$hcount - 1] == "F" && $map[$vcount + 1][$hcount] == "F" && 
                $map[$vcount + 1][$hcount + 1] == "F" && $map[$vcount + 2][$hcount] == "F")
                echo "Pattern found, starting at : (v)$vcount x (h)$hcount";
        }
    }
}

$> php test.php
php test.php
Pattern found, starting at : (v)18 x (h)8
Pattern found, starting at : (v)22 x (h)30
$>

But I must admit that it could take a while for extra-big maps.

/!\ add some code to verify that the line $vcount + 1/2 actually exists, and the char $hcount + 1 too.

回答2:

You can use $length=strstr($inputmap,"\n") to find the width of each line. You can then construct a regular expression that will find an F, followed by ($length-2) other characters, followed by 3 Fs, followed by ($length-2) other characters, followed by an F.

回答3:

You could use the following code:

$lines = array_filter(preg_split("#\r\n?|\n#", $string)); // Creating array of lines
$matrix = array_map('str_split', $lines); // Creating a matrix

foreach($lines as $line_number => $line_content){ // Looping through the lines
    $pos = strpos($line_content, 'FFF');
    if(!$pos === false){// If FFF found
        while(true){
            if(isset($matrix[$line_number-1][$pos+1],$matrix[$line_number+1][$pos+1]) && $matrix[$line_number-1][$pos+1] == 'F' && $matrix[$line_number+1][$pos+1] == 'F'){ //Checking ...
                echo 'Found at: X:'.$pos.' & Y:'.$line_number.'<br>'; // Ouput
            }
            $pos = strpos($line_content, 'FFF', $pos+1); // Search further
            if(!is_int($pos)){
                break;
            }
        }
    }
}

What's going on ?

We create an array of lines
We create a matrix
We loop through the lines and search for FFF this is to increase performance. So instead of looping through the whole matrix and searching for F, we directly search for FFF
Check if the value exists in the matrix (to prevent undefined index errors) and then check if it equals F
Output
Search further on the same line

Online demo

_{Note that the coordinates are the center of the +}

回答4:

try with this pattern:

if the end of line is \n:

$pattern = '~F.{'. ($n-2) . '}FFF.{' . ($n-2) . 'F~s';

if the end of line is \r\n then replace by $n-3

or better use quinxorin trick to know the line length until the \n

回答5:

@FrankieTheKneeMan & all... my initial approach was to build 'n' regular expression for 'n' chars of the input grid map. Something like...

$search_001 = "
.F......................................
FFF.....................................
.F......................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
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........................................
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........................................
........................................
........................................
";


$search_002 = "
..F.....................................
.FFF....................................
..F.....................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
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........................................
........................................
........................................
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........................................
........................................
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........................................
........................................
";

(... omissis ...)

$search_100 = "
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
..........F.............................
.........FFF............................
..........F.............................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
";

(... omissis ...)

$search_999 = "
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
........................................
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........................................
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........................................
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........................................
........................................
........................................
........................................
........................................
........................................
......................................F.
.....................................FFF
......................................F.
";

where "." obvioulsy means any character.

Is this a stupid idea?!?

来源：https://stackoverflow.com/questions/17026462/php-vertical-regular-expression-search

标签

php

regex

pattern-matching