<?php
function is_valid($string) {
while (($string = preg_replace('~(?:\(\)|\{}|\[])+~', '', $string, -1, $count)) && $count);
return (int)!$string;
}
$expressions = array(")(){}", "[]({})", "([])", "{()[]}", "([)]", "{()[]}{()[]}{()[]}{()[]}{()[]}");
foreach ($expressions as $expression) {
echo "$expression is " , is_valid($expression) , "\n";
}
preferences:
23.67 ms | 404 KiB | 5 Q