Can the for loop be eliminated from this piece of PHP code?

Question

I have a range of whole numbers that might or might not have some numbers missing. Is it possible to find the smallest missing number without using a loop structure? If ther

Answer 1

$range = array(0,1,2,3,4,6,7);

$max=max($range);

$expected_total=($max*($max+1))/2; // sum if no number was missing.

$actual_total=array_sum($range);  // sum of the input array.

if($expected_total==$actual_total){
   echo $max+1;      // no difference so no missing number, then echo 1+ missing number.
}else{
   echo $expected_total-$actual_total; // the difference will be the missing number.
}