Detect overlapping periods php

Question

can you help me with overlapping periods. I have array

["1-9","11-15","14-20","8-11"]

Each element in array its period. Min - 1 period, max - 10 periods in array. I need to detect if they are overlapping.

I find this cases from another question

https://stackoverflow.com/questions/325933/determine-whether-two-date-ranges-overlap — Klemen Tusar, Jun 13 '16 at 11:18
is your question how to understand that to element are overlapping? — splash58, Jun 13 '16 at 11:19
@Vladislav do you want to check that overlapping is, or find overlapped items ? — splash58, Jun 13 '16 at 12:00

score 0 · Accepted Answer · answered Jun 13 '16 at 11:53

This is a simple snippet that way of its checking is based on comparing highest end of first range to lowest end of second range (if we only consider that ranges are valid). And at the first place, sorting ranges is playing an important role:

$ranges = ["1-9","11-15","14-20","8-11"];
$results = [];
sort($ranges, SORT_NUMERIC);
foreach ($ranges as $first) {
    $firstNums = explode("-", $first);
    foreach ($ranges as $second) {
        if ($first == $second) continue;
        $secondNums = explode("-", $second);
        if ($firstNums[1] >= $secondNums[0] && $first != end($ranges)) {
            $results[$first] = $second;
        }
    }
}
print_r($results);

Results (which contain both dates that overlap):

Array
(
    [1-9] => 8-11
    [8-11] => 11-15
    [11-15] => 14-20
)

I used `>=` comparison operator which you may change it to only a `>` one. — revo, Jun 13 '16 at 12:04

axelvnk · Answer 2 · 2019-10-28T13:07:01.283

This should cover all the scenarios :

<?php

public function findOverlappingPeriods(array $periods): array
{
    $overlappingItems = [];

    foreach ($periods as $keyA => $periodA) {
        foreach ($periods as $keyB => $periodB) {
            if ($keyA === $keyB) {
                continue;
            }

            if ($periodB['start'] > $periodA['start'] && $periodB['start'] < $periodA['end']) {
                $overlappingItems[] = $keyA;
                $overlappingItems[] = $keyB;
            }
        }
    }

    return $overlappingItems;
}

Detect overlapping periods php

2 Answers2