How to get the greatest difference among a list of ordered numbers in PHP?

Question

For example,

1,3,6,8,11,45,99

The interval between numbers is:

2,3,2,3,34,54

So the greatest difference is 54.

How to implement this function?

function get_greatest_diff($arr_of_numbers)
{}

Answer 1

You got a lot of different options:

• Sort the array, then compare the first and the last element
• For each element, compare it to each subsequent element. Keep the highest difference in memory.
• Implement some kind of merge-sort, but return the difference instead of the original sorted values.

Answer 2

You should handle the case where the array has less than 2 elements separately:

$maxDiff = -1;
for ($i = 0; $i + 1 < count($array); $i++) {
    $diff = $array[$i + 1] - $array[$i];
    if ($diff > $maxDiff)
        $maxDiff = $diff;
    }
}

Answer 3

You should do something like this :

$greatest_diff = 0;

for($i = 0; $i < sizeof($arr_of_numbers) - 1; $i++)
{
    $current_diff = $arr_of_numbers[$i + 1] - $arr_of_numbers[$i];
    if($current_diff > $greatest_diff){
        $greatest_diff = $current_diff;
    }
}

echo $greatest_diff;