How to find missing values in a sequence with PHP?

Question

Suppose you have an array \"value => timestamp\". The values are increasing with the time but they can be reset at any moment.

For example :

$array = arr         


        

Answer 1

You can do the following:

• Keep comparing adjacent array keys. If they are consecutive you do nothing.
• If they are not consecutive then you check their values, if the value has dropped from a higher value to a lower value, it means there was a reset so you do nothing.
• If the value has not dropped then it is a case of missing key(s). All the numbers between the two keys(extremes not included) are part of the result.

Translated in code:

$array = array( 1 => 6000, 2 => 7000, 3 => 8000, 7 => 9000, 8 => 10000, 
                9 => 11000,55 => 1000, 56 => 2000, 57 => 3000, 59 => 4000, 
                60 => 5000,);

$keys = array_keys($array);
for($i=0;$i

Working link