Question

How to find the longest repeating substring in a string with PHP

Answer 1

function longestCommonPrefix($sub1, $sub2) {
    $min = min(strlen($sub1), strlen($sub2));
    
    for ($i = 0; $i < $min; $i++) {
        if ($sub1[$i] != $sub2[$i]) {
            return substr($sub1,0,$i - 0);
        }
    }
    return substr($sub1,0,$min - 0);
}

function longestRepeatingSubstring($s) {
    $lrs = "";
    $size = strlen($s);
    
    for ($i = 0; $i < $size; $i++) {
        for ($j = $i + 1; $j < $size; $j++) {
            $lcp = longestCommonPrefix(substr($s,$i,$size - $i), substr($s,$j,$size - $j));
            if (strlen($lcp) > strlen($lrs)) {
                $lrs = $lcp;
            }
        }
    }
    return $lrs;
}
        
$s = "pythonphpjavacdartcppjavacsharp";

echo longestRepeatingSubstring($s);




/*
run:

pjavac

*/

 

70+ SQL courses for beginners and professionals