Question

How to find the longest substring without repeating characters in PHP

Answer 1

function findLongestSubstringWithoutRepeatingCharacters($str) {
    $str_size = strlen($str);
    $start = 0;
    $end = 0;
    $start_sub = 0;
    $end_sub = 0;
        
    // array_fill(int $start_index, int $count, mixed $value): array
    $ASCII = array_fill(0, 256, 0);
    
    while ($end < $str_size) {
        if ($ASCII[ord($str[$end])] > 0) {
            while ($str[$start] != $str[$end]) {
                $ASCII[ord($str[$start])] = 0;
                $start++;
            }
            $start++;
        }
        else {
            $ASCII[ord($str[$end])] = $end + 1;
            if ($end - $start > $end_sub - $start_sub) {
                $start_sub = $start;
                $end_sub = $end;
            }
        }
        $end++;
    }
    for ($i = $start_sub; $i <= $end_sub; $i++) {
        echo $str[$i];
    }
}


$str = "xwwwqfwwxqwyq";

findLongestSubstringWithoutRepeatingCharacters($str);




/*
run:

xqwy

*/

 

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