pedmillon - 4 months ago 13

PHP Question

I have such an array of intervals sorted by the lower bound ($a[$i] <= $a[$i+1] for every $i), key *l* is lower bound and , key *h* is upper bound and I'd like to remove all rows with intervals that are enclosed by larger intervals.

`$a[0] = array('l' => 123, 'h'=>241);`

$a[1] = array('l' => 250, 'h'=>360);

$a[2] = array('l' => 280, 'h'=>285);

$a[3] = array('l' => 310, 'h'=>310);

$a[4] = array('l' => 390, 'h'=>400);

So the result I'd like to get is

`$a[0] = array('l' => 123, 'h'=>241);`

$a[1] = array('l' => 250, 'h'=>360);

$a[2] = array('l' => 390, 'h'=>400);

This is what I attempted

`function dup($a){`

$c = count($a)-1;

for ($i = $c; $i > 0; $i --){

while ($a[$i]['h'] <= $a[$i-1]['h']){

unset($a[$i]);

}

}

$a = array_values($a);

}

Answer

A simplistic approach, maybe not exactly what you want, but should at least point you in the right direction. I can refine it if needed, just a bit busy and didn't want to leave the question unanswered..

```
$out = [];
foreach ($a as $valA)
{
$found = false;
foreach ($a as $valB)
{
if (($valA['l'] > $valB['l']) && ($valA['h'] < $valB['h']))
{
$found = true;
break;
}
}
if (!$found)
{
$out[] = $valA;
}
}
```

This is entirely untested, but should end up with only the unique (large) ranges in $out. Overlaps as I mentioned in my comment are unhandled.