Implode sorted number array to string by commas and merge intervals

Question

I would like to implode an array, but with one difference. I would like to merge intervals with a - sign. How can this be done? (The array is ordered!)

Answer 1

    $oldArray=array(2,4,5,6,8,10);

    $newArray=array();


    foreach($oldArray as $count=>$val){
        if($count==0){
            //begin sequencing
            $sequenceStart=$sequenceEnd=$val;
        }

        if($val==$sequenceEnd+1){
            $sequenceEnd=$val;
            continue;
        }else{
            if($sequenceEnd==$val){
                //do nothing
                continue;
            }


        }

        //new sequence begins 
        //save new sequence
        if($sequenceStart==$sequenceEnd){
            //sequnce is a single number
            $newArray[]=$sequenceEnd;
        }else{
            $newArray[]=$sequenceStart.'-'.$sequenceEnd;
        }

        //reset sequence
        $sequenceStart=$sequenceEnd=$val;
    }

    //new sequence begins 
    //save new sequence
    if($sequenceStart==$sequenceEnd){
        //sequnce is a single number
        $newArray[]=$sequenceEnd;
    }else{
        $newArray[]=$sequenceStart.'-'.$sequenceEnd;
    }

    //reset sequence
    $sequenceStart=$sequenceEnd=$val;



    return implode(',', $newArray);

Answer 2

There is no function like this, therefore you will need to create one yourself. I just created a sample function how this may look like, there are many possible solution for this (Did not try if it actually works, as I do not have a webserver in reach atm)

<?php
function implodeNumberArray($arr) {
 $lastValue = NULL;
 $o = "";
 //For each value in array
 foreach ($arr as $v) {
  if(!is_null($lastValue)) {
   //If the number is following, do not paste it
   if(($lastValue+1) == $v) {
    //Check if the - sign was already posted
    if(!(stripos(strrev($o), '-') === 0)) {
     // - sign not pasted, therefore paste it
     $o .= "-";
    }
   } else {
    //Check if there is a - sign at the end
    if((stripos(strrev($o), '-') === 0)) {
     // Has - => paste 'prevValue,value''
     $o .= $lastValue . "," . $v;
    } else {
     //Check if there is a , sign at the end
     if((stripos(strrev($o), ',') === 0)) {
      // No - but , => paste 'value'
      $o .= $v;
     } else {
      // No - and no , => paste ',value'
      $o .= ",".$v;
     }         
    }
   }
  } else {
   $o = $v;
  }

  $lastValue = $v;
 }
 //Check if the implode has the last number set correctly
 if((stripos(strrev($o), '-') === 0)) {
  $o .= $lastValue;
 }
 return $o;
}

echo implodeNumberArray(array(1,2,3,6,8,9));
?>

Answer 3

This should work for you:

First for every iteration we simply append the current number of the iteration to the $result string:

$result .= $arr[$i];

After this we check in a while loop if there exists a next element in the array(1) and it follows up the number from the current iteration(2). We do that until the condition evaluates as false:

//(1)Check if next element exists     (2)Check if next element follows up the prev one
      ┌───────┴───────┐    ┌───────────┴────────────┐      
while(isset($arr[$i+1]) && $arr[$i] + 1 == $arr[$i+1] && ++$range)
    $i++;

Then we check if we have a range (e.g. 1-3) or not. If yes then we append the dash and the end number of the range to the result string:

if($range)
    $result .= "-" . $arr[$i];

At the end we also check if we are at the end of the array and don't need to append a comma anymore:

if($i+1 < $l)
    $result .= ",";

Code:

<?php

    $arr = array(1,2,3,6,8,9);
    $result = "";
    $range = 0;

    for($i = 0, $l = count($arr); $i < $l; $i++){

        $result .= $arr[$i];

        while(isset($arr[$i+1]) && $arr[$i] + 1 == $arr[$i+1] && ++$range)
            $i++;

        if($range)
            $result .= "-" . $arr[$i];

        if($i+1 < $l)
            $result .= ",";

        $range = 0;   

    }

    echo $result;

?>

output:

1-3,6,8-9