Php string with separator to page list - php

Question

I try to recreate what we see when we printing page on office or adobe.
For example, when you want to print page 1 to 5 you write : 1-5 and if you want to print a page outside you write : 1-5,8
At the moment I explode string by ',' :
1-5 / 8
Then explode each result by '-' and if I've got result I loop from first page to last and create variable with comma :
1,2,3,4,5,8
Finally I explode by ',' and use array unique to erase double value.
It take some times to achieve this especially when there's a lot of '-'.
Maybe someone got a easier solution to so this ?
Thank
Edit :
$pages = "1-4,6-8,14,16,18-20";
$pages_explode = explode(',',$pages);
foreach($pages_explode as $page){
$page_explode = explode('-',$page);
if(!empty($page_explode[1])){
for ($i=$page_explode[0]; $i<=$page_explode[1] ; $i++) {
$page_final .= $i.',';
}
}else{
$page_final .= $page_explode[0].',';
}
}
$page_final = explode(',',$page_final);
$page_final = array_unique ($page_final);
foreach($page_final as $value){
echo $value.'<br>';
}

Answer 1

Is it a code golf challenge?
Well a basic approach seems fine to me :
$input = '1-5,6-12,8';
$patterns = explode(',', $input);
$pages = [];
foreach ($patterns as $pattern) {
if (2 == count($range = explode('-', $pattern))) {
$pages = array_merge($pages, range($range[0], $range[1]));
} else {
$pages[] = (int)$pattern;
}
}
$uniquePages = array_unique($pages);
var_dump($uniquePages);
Outputs :
array (size=12)
0 => int 1
1 => int 2
2 => int 3
3 => int 4
4 => int 5
5 => int 6
6 => int 7
7 => int 8
8 => int 9
9 => int 10
10 => int 11
11 => int 12

Answer 2

Having to remove duplicates suggests that you have overlapping ranges in your strings.
Eg: 1-5,2-9,7-15,8,10
You seems to process all these without considering the overlapping areas and finally attempt to remove duplicates by the expensive array_unique function.
Your code should instead remember the minimum and maximum of the resulting range and not process anything that overlaps this range.
Following is a sample code which demonstrates the idea. But its certainly faster than the code you have suggested in your question. You should add parts there to process additional types of delimiters, if any, in your requirement.
<?php
$ranges = "1-5,3-7,6-10,8,11";
$min = 10000;
$max = -1;
$numbers = array(); //Your numbers go here
//Just a utility function to generate numbers from any range and update margins
function generateNumbers($minVal, $maxVal) {
global $min, $max, $numbers;
for ($i = $minVal; $i <= $maxVal; $i++) {
array_push($numbers, $i);
if ($i < $min)
$min = $i;
if ($i > $max)
$max = $i;
}
}
//Seperate ranges
$sets = explode(",", $ranges);
//Go through each range
foreach($sets as $aSet) {
//Extract the range or get individual numbers
$range = explode("-", $aSet);
if (count($range) == 1) { //its an individual number. So check margins and insert
$aSet = intval($aSet);
if ($aSet < $min){
array_push($numbers, $aSet);
$min = $aSet;
}
if ($aSet > $max){
array_push($numbers, $aSet);
$max = $aSet;
}
continue; // <----- For single numbers it ends here
}
//Its a range
$rangeLow = intval($range[0]);
$rangeHigh = intval($range[1]);
//Adjusting numbers to omit cases when ranges fall right on the margins
if ($rangeLow == $min){
$rangeLow++;
}
else
if ($rangeLow == $max) {
$rangeLow--;
}
if ($rangeHigh == $min){
$rangeHigh++;
}
else
if ($rangeHigh == $max) {
$rangeHigh--;
}
//Check if below or above the generated range
if (($rangeLow < $min && $rangeHigh < $min) || ($rangeLow > $max && $rangeHigh > $max)) {
generateNumbers($rangeLow, $rangeHigh);
};
//Check if across the lower edge of the generated range
if ($rangeLow < $min && $rangeHigh > $min && $rangeHigh < $max) {
generateNumbers($rangeLow, $min - 1);
};
//Check if across the upper edge of the generated range
if ($rangeLow > $min && $rangeLow < $max && $rangeHigh > $max) {
generateNumbers($max + 1, $rangeHigh);
};
}
//Now just sort the array
print_r($numbers);
?>