Question

How I can change this:

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 11
    [8] => 21
    [9] => 22
    [10] => 23
    [11] => 24
)

To this:

1-7, 11, 21-24

I have a list of numbers like this in PHP array, and I just want to make this list a little bit smaller.

2000: 3 6 7 11 15 17 25 36 42 43 45
2001: 2 3 4 5 6 9 10 11 12 13 34 37 45 46 47 48 49 50 51 52
2002: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 33 34 35 36 37 39 40 41 42 43 44 45 46 47 48 49 50 51 52
2003: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
2004: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 16 17 18 19 21 22 23 24 25 26 27 28 29 30 31 32 33 34 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
2005: 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
2006: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
2007: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

Answer 1

Interesting task.

Here’s a demo script that does exactly what you want.

Tweak to taste.

Code

<?php

$groups = array();
$active_group = 0;

$output = array();
$output_counter = 0;

$nums = array( 1, 2, 3, 4, 5, 6, 7, 11, 21, 22, 23, 24 );


foreach( $nums as $k => $num ) {

    // if this isn't the first item, and the current number
    // isn't one more than the previous one, increment the counter
    if( $k !== 0 && $nums[$k] !== $nums[$k-1]+1 )
        $active_group ++;

    // add this number to a group
    $groups[ $active_group ][] = $num;

}


// take the 1st and last of each group
foreach( $groups as $group ) {

    $first = array_shift( array_values($group) );
    $output[$output_counter][] = $first;

    $last = array_pop( array_values($group) );
    if( $first !== $last )
        $output[$output_counter][] = $last;

    $output_counter++;

}


echo '<pre>';
print_r($output);

?>

Output

Array
(
    [0] => Array
        (
            [0] => 1
            [1] => 7
        )

    [1] => Array
        (
            [0] => 11
        )

    [2] => Array
        (
            [0] => 21
            [1] => 24
        )

)