CODEWITHSUNDEEP
phparrays
Jack33
Jack33

Reputation: 121

Convert array with numbers to sequences and single numbers

I have an array:

$array = [1, 2, 3, 4, 6, 7, 8, 10, 12, 14, 15, 16, 20, 21, 26, 27, 28];

and I want to convert it to a string where sequences are seperated by a dash. So the above array would become: 1-4, 6-8, 10, 12, 14-16, 20, 21, 26-28

I have tried looping through an error and checking of the previous number + 1 is equal to the current number to determine if I'm in a loop. Didn't quite manage it and it felt very inefficient. Any tips and/or ideas on how to fix this?

This code is unfinished and not working completely:

asort($zips);

$formatted = '';
$sequence = [];
$inSequenceLoop = false;

foreach ($zips as $key => $zip) {

//    $prev = $key === 0 ? false : $zips[$key - 1];
    $current = $zip;
    $next = $key === count($zips) - 1 ? false : $zips[$key + 1];

    if ($current + 1 === $next) {// || ($next === false && ($prev + 1) === $current)) {
        $sequence[] = $current;
        $inSequenceLoop = true;
    } else {
        if ($inSequenceLoop) {
            // end of sequence
            if (count($sequence) === 1) {
                $formatted .= $sequence[0] . ($next ? ',' : '');
            } else {
                $formatted .= array_shift($sequence) . '-' . array_pop($sequence) . ($next ? ',' : '');
            }

            // create empty sequence
            $inSequenceLoop = false;
            $sequence = [];
        } else {
            // loner
            $formatted .= $current . ($next ? ',' : '');
        }
    }
}

Upvotes: 2

Views: 375

Answers (1)

Don't Panic
Don't Panic

Reputation: 41810

One approach would be to first split the array into sets:

$pre = $key = 0;                      // initialize previous value and set key

foreach ($array as $number) {
    if ($number > $pre + 1) $key++;   // if number is not next in sequence, increment key
    $sets[$key][] = $pre = $number;   // append to current key and set previous to current
}

then map a formatting function to return the range strings, and implode the formatted ranges.

$result = implode(', ', array_map(function($set) {
    // return either single element or dash separated first and last element
    return count($set) == 1 ? reset($set) : reset($set) . '-' . end($set);
}, $sets));

If a range of two elements should be formatted as individual elements, the format function could take that into account as well.

$result = implode(', ', array_map(function($set) {
    switch (count($set)) {
        case 1: return reset($set);
        case 2: return reset($set) . ', ' . $set[1];
        default: return reset($set) . '-' . end($set);
    }
}, $sets));

Upvotes: 1

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