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<?php function is_valid($string) { return preg_match('~(\((?1)*+\)|\[(?1)*+]|{(?1)*+})*\z~A', $string); } $expressions = array(")(){}", "[]({})", "([])", "{()[]}", "([)]", "{()[]}{()[]}{()[]}{()[]}{()[]}"); foreach ($expressions as $expression) { echo "$expression is " , is_valid($expression) , "\n"; }
Output for 5.6.38, 7.1.0 - 7.1.23, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
)(){} is 0 []({}) is 1 ([]) is 1 {()[]} is 1 ([)] is 0 {()[]}{()[]}{()[]}{()[]}{()[]} is 1
preferences:
166.13 ms | 408 KiB | 5 Q