Best way to return the first repeated element of array

Question

This is an interview question:

What is the best way to return the first repeated element out of the array of integers?

Example:

Given an array [12, 46, 244, 0, 12, 83, 48, 98, 233, 83, 26, 91, 119, 148, 98].

The return value in this case is 12.

How can this be done?

Answer 1

i think that if you look of performance, foreach loop is the faster

# temp array
$array_help = array();

# run over the array
foreach ($array as $val) {

    if (isset($array_help[$val]))
     # found if is set already !
        return $val;

    else
       # its the first time this value appear
       $array_help[$val] = 1;
}

Answer 2

This will give you all the duplicate values and their original positions:

$diff = array_diff_assoc($array, array_unique($array));
var_dump($diff);

result:

array(3) { 
  [4]=> int(12) 
  [9]=> int(83)
  [14]=> int(98) 
}