Question

How to find the smallest missing number from sorted list in PHP

Answer 1

function findSmallestMissingNumber($arr) {
    $min = $arr[0];
    $size = count($arr);
    
    for ($i = 1; $i < $size; $i++) {
        if ($arr[$i] > $min + 1) {
            return $min + 1;
        }
        else {
            $min = $arr[$i];
        }
    }
    
    return -1;
}

$arr = array(18, 19, 20, 27, 33, 36, 40, 42);
        
echo findSmallestMissingNumber($arr);





/*
run:

21

*/

 

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