solution for https://www.hackerrank.com/challenges/sock-merchant/

sock-merchant.php

<?php

// Complete the sockMerchant function below.
function sockMerchant($n, $ar) {
    $arnew = array();
    $cnt=0;
    foreach($ar as $val){
        if (isset($arnew[$val])){
            $cnt++;
            unset($arnew[$val]);
        }
        else{
            $arnew[$val]=1;
        }
    }
    return $cnt;
}

$fptr = fopen(getenv("OUTPUT_PATH"), "w");

$stdin = fopen("php://stdin", "r");

fscanf($stdin, "%d\n", $n);

fscanf($stdin, "%[^\n]", $ar_temp);

$ar = array_map('intval', preg_split('/ /', $ar_temp, -1, PREG_SPLIT_NO_EMPTY));

$result = sockMerchant($n, $ar);

fwrite($fptr, $result . "\n");

fclose($stdin);
fclose($fptr);

How??? does this work? It passes all tests!