patternphpMinor

Aggregate array values into ranges

Submitted by: @import:stackexchange-codereview·Mar 10, 2026·

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arrayintorangesvaluesaggregate

Problem

In five minutes I made a pretty ugly looking function. Can you help before I have to commit the code into history?

Requirements:

I would like a function that takes an array of numbers, and returns an
array of ranges. Ideally remove the duplicate line.

Sample Input:

Array(1,2,3,4,5,6,10,11,12,13,20,24)

Output:

Array
(
    [0] => 1-6
    [1] => 10-13
    [2] => 20
    [3] => 24
)

Winning Entries:

Pseudo code  
PHP

My attempt:

$myArray = array(1,2,3,4,5,6,10,11,12,13,20,24);

$rangeArray = array();
$start = $end = current($myArray);
foreach($myArray as $range){
    if($range - $end > 1){
        $rangeArray[] = ($start == $end)?$start:$start."-".$end;
        $start = $range;
    }

    $end = $range;
}
$rangeArray[] = ($start == $end)?$start:$start."-".$end;

print_r($rangeArray);

Solution

While these may not be any shorter or more efficient than existing answers, perhaps with a slightly different approach they still bring something to the table and might be considered a little less 'ugly'.

Essentially the GetRanges function I've written does the following:

-
Take a parameter-supplied array of numbers ($aNumbers), remove any duplicates from the array and then sort them numerically lowest to highest.

-
We next create a multi-dimensional array ($aGroups) and working sequentially through the array of numbers ($aNumbers): Except for the first number which we just add to $aGroups to get us started, for each consecutive number $i > 0, if the previous number $aNumbers[$i-1] is equal to the current number minus 1 $aNumbers[$i] - 1 then the current number is added to the same group because its consecutive and belongs to that range, otherwise the current number is added to $aGroups as a new sub-array with one entry array( $aNumbers[$i] ).

For options 2 and 3 where the function is expanded upon for a simple array:

A new array ($aRanges) is created and for each $aGroups record, if the first entry of the sub-array is the only entry then a new entry is added to $aRanges for just this number, otherwise a new entry is added to $aRanges specifying the first number in the range followed by a hyphen followed by the last number in the range.

For option 3 where the function is expanded upon to return a string:

The implode function is used to create a comma-separated list of all the entries in the $aRanges array and return this as a string.

Option 1: If you want your function to return a multi-dimensional array:

 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  return $aGroups;
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
print_r( GetRanges( $aNumbers ));

Output:

Array (
  [0] => Array ( [0] => 1, [1] => 2, [2] => 3, [3] => 4, [4] => 5, [5] => 6 )
  [1] => Array ( [0] => 10, [1] => 11, [2] => 12, [3] => 13 )
  [2] => Array ( [0] => 20 )
  [3] => Array ( [0] => 24 )
)

Option 2: If you want your function to return a simple array:

 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  $aRanges = array();
  foreach( $aGroups as $aGroup ) {
    if( count( $aGroup ) == 1 )
      $aRanges[] = $aGroup[0];
    else
      $aRanges[] = $aGroup[0] . '-' . $aGroup[count($aGroup)-1];
  }
  return $aRanges;
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
print_r( GetRanges( $aNumbers ));

Output: Array ( [0] => 1-6, [1] => 10-13, [2] => 20, [3] => 24 )

Option 3: If you want your function to return a string:

 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  $aRanges = array();
  foreach( $aGroups as $aGroup ) {
    if( count( $aGroup ) == 1 )
      $aRanges[] = $aGroup[0];
    else
      $aRanges[] = $aGroup[0] . '-' . $aGroup[count($aGroup)-1];
  }
  return implode( ',', $aRanges );
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
echo( GetRanges( $aNumbers ));

Output:
1-6,10-13,20,24

Code Snippets

<?php
function GetRanges( $aNumbers ) {
  $aNumbers = array_unique( $aNumbers );
  sort( $aNumbers );
  $aGroups = array();
  for( $i = 0; $i < count( $aNumbers ); $i++ ) {
    if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  return $aGroups;
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
print_r( GetRanges( $aNumbers ));

Array (
  [0] => Array ( [0] => 1, [1] => 2, [2] => 3, [3] => 4, [4] => 5, [5] => 6 )
  [1] => Array ( [0] => 10, [1] => 11, [2] => 12, [3] => 13 )
  [2] => Array ( [0] => 20 )
  [3] => Array ( [0] => 24 )
)

<?php
function GetRanges( $aNumbers ) {
  $aNumbers = array_unique( $aNumbers );
  sort( $aNumbers );
  $aGroups = array();
  for( $i = 0; $i < count( $aNumbers ); $i++ ) {
    if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  $aRanges = array();
  foreach( $aGroups as $aGroup ) {
    if( count( $aGroup ) == 1 )
      $aRanges[] = $aGroup[0];
    else
      $aRanges[] = $aGroup[0] . '-' . $aGroup[count($aGroup)-1];
  }
  return $aRanges;
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
print_r( GetRanges( $aNumbers ));

<?php
function GetRanges( $aNumbers ) {
  $aNumbers = array_unique( $aNumbers );
  sort( $aNumbers );
  $aGroups = array();
  for( $i = 0; $i < count( $aNumbers ); $i++ ) {
    if( $i > 0 && ( $aNumbers[$i-1] == $aNumbers[$i] - 1 ))
      array_push( $aGroups[count($aGroups)-1], $aNumbers[$i] );
    else
      array_push( $aGroups, array( $aNumbers[$i] )); 
  }
  $aRanges = array();
  foreach( $aGroups as $aGroup ) {
    if( count( $aGroup ) == 1 )
      $aRanges[] = $aGroup[0];
    else
      $aRanges[] = $aGroup[0] . '-' . $aGroup[count($aGroup)-1];
  }
  return implode( ',', $aRanges );
}

$aNumbers = array( 1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 20, 24 );
echo( GetRanges( $aNumbers ));

Context

StackExchange Code Review Q#80080, answer score: 5

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