Small sorting algorithm in php

Question

It should quite simple algorithm, but I just can't get around it.

I have some arrays in alphabetical order

[0] => Array
    (
        [0] => a
        [1] => b
        [2] => c
    )

and for example

[0] => Array
    (
        [0] => a
        [1] => b
        [2] => c
        [3] => d
    )

and I need to sort them into rows. For example:

I should receive a table with 3 columns and as many rows as it may get and it should be in alphabetical order.

Here is an example: First array should be converted into

[0] => Array
    (
        [0] => Array
            (
                [0] => a
                [1] => b
                [2] => c
            )

    )

But second one should be as

[1] => Array
    (
        [0] => Array
            (
                [0] => a
                [1] => c
                [2] => d
            )
        [1] => Array
            (
                [0] => b
            )
    )

I'm writing it in php, so if anyone can help I would be really appreciated.

UPD: Code example:

function sortAsOrdered( array $categories )
{
    foreach ( $categories as $groupId => $group )
    {
        $regroupMenuItems = array();
        $limit            = count( $group );
        $rows             = ceil( $limit / 3 );

        for ( $i = 0; $i < $rows; ++$i )
        {
            $jumper = 0;

            for ( $j = 0; $j < 3; $j++ )
            {
                if ( 0 == $jumper )
                {
                    $jumper = $i;
                }

                if ( isset( $group[ $jumper ] ) )
                {
                    $regroupMenuItems[ $i ][ $j ] = $group[ $jumper ];
                }

                $jumper = $jumper + $rows;
            }
        }

        $categories[ $groupId ] = $regroupMenuItems;
    }

    return $categories;
}

Guys I solved this one. Here you could see my algorithm http://pastebin.com/xe2yjhYW. But don't be sad your help will not go in vain. I probably will place bounty just for those who helped with this dificult algorithm for me.

Guys thanks one more time. Your thoughts inspired me to think differently.

Answer 1

array_chunk() wold have been the solution but as you want it to be specially sorted, that wouldn't help you much.

So here is my five cents:

function array_chunk_vertical($input, $size_max) {
    $chunks = array();
    $chunk_count = ceil(count($input) / $size_max);

    $chunk_index = 0;
    foreach ($input as $key => $value) {
        $chunks[$chunk_index][$key] = $value;

        if (++$chunk_index == $chunk_count) {
            $chunk_index = 0;
        }
    }

    return $chunks;
}


$array = array('a', 'b', 'c', 'd', 'e', 'f');
var_dump(array_chunk_vertical($array, 2));

Which will give you:

array
  0 => 
    array
      0 => string 'a' (length=1)
      3 => string 'd' (length=1)
  1 => 
    array
      1 => string 'b' (length=1)
      4 => string 'e' (length=1)
  2 => 
    array
      2 => string 'c' (length=1)
      5 => string 'f' (length=1)

The downside of this function is that you can only tell the max number of elements in a chunk, and then it equally divides the array to chunks. So for [4] and max_size 3 you will get [2,2] unlike the expected [3,1].

Answer 2

Let's see if this is nearer the mark

function splitVerticalArrayIntoColumns($aInput, $iNumberOfColumns) {

  //output array
  $aOutput = array();

  //the total length of the input array
  $iInputLength = count($aInput);

  //the number of rows will be ceil($iInputLength / $iNumberOfColumns)
  $iNumRows = ceil($iInputLength / $iNumberOfColumns);

  for($iInputIndex = 0; $iInputIndex < $iInputLength; $iInputIndex++) {
    $iCurrentRow = $iInputIndex % $iNumRows;
    $aOutput[$iCurrentRow][] = $aInput[$iInputIndex];
  }

  //return
  return $aOutput;
}

Which - when run thus:

$aList = array("a", "e", "d", "b", "c");
echo 'array("a", "e", "d", "b", "c")' . "\n\n";
print_r(splitVerticalArrayIntoColumns($aList, 3));

Gives:

array("a", "e", "d", "b", "c")

Array
(
    [0] => Array
        (
            [0] => a
            [1] => d
            [2] => c
        )

    [1] => Array
        (
            [0] => e
            [1] => b
        )

)

That's not sorting each row yet but is that the kind of thing you're after?

---

---

begin facepalm edit

... or of course, array_chunk($aList, 3) after you've sorted it O_o

http://uk3.php.net/manual/en/function.array-chunk.php

I'll leave everything below for reference or whatever - I'd completely forgotten about array_chunk()

end facepalm edit

---

I'd use a modulo in a loop where you're counting the array index (after sorting the array) - for instance if you're trying to split an array into 3 "columns" you could try something like:

if($iIndex % 3 == 0) {
  //... create a new array
}
else {
  //... add to an existing array
}

EDIT code example:

$aList = array("a", "e", "d", "b", "c");
sort($aList);

$iDesiredNumberOfColumns = 3;
$iListLength = count($aList);

$aListInColumns = array();
$iRowNumber = 0;

for($iIndex = 0; $iIndex < $iListLength; $iIndex++) {
  $iColumnNumber = $iIndex % 3;
  if($iIndex != 0 && $iColumnNumber == 0) {
    $iRowNumber++;
  }

  $aListInColumns[$iRowNumber][$iColumnNumber] = $aList[$iIndex];
}

Just ran it on my local server (and corrected the typo), and it outputs as:

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
            [2] => c
        )

    [1] => Array
        (
            [0] => d
            [1] => e
        )

)

There's probably a tidier way of doing it (that's a little procedural) but it should do the job.

Answer 3

<?php

$five_el = array('a', 'b', 'c', 'd', 'e');

$two_el = array('a', 'b');

$three_el = array('a', 'b', 'c');

$six_el = array('a', 'b', 'c', 'd', 'e', 'f');

function multid($sorted_array) {
    $mulidarray = array();
    $row = 0;
    $column = 0;
    foreach ($sorted_array as $value) {
        if ($column == 3) {
            $row++;
        }
        $column++;
        if (!isset($mulidarray[$row])) {
            $mulidarray[$row] = array();
        }
        $multidarray[$row][] = $value;
    }

    return $multidarray;
}

var_dump(multid($five_el));
var_dump(multid($two_el));
var_dump(multid($three_el));
var_dump(multid($six_el));

Answer 4

array_chunk is a natural first approach to the problem, but it won't do exactly what you need to. If the solution is provided that way, you need to either restructure the resulting array or restructure the input before processing it, as below:

$input = range('a', 'k');  // arbitrary
$columns = 3;  // configure this
$rows = ceil(count($input) / $columns);

// fugly, but this way it works without declaring a function
// and also in PHP < 5.3 (on 5.3 you'd use a lambda instead)
$order = create_function('$i',
                         '$row = (int)($i / '.$rows.');'.
                         '$col = $i % '.$rows.';'.
                         'return $col * ('.$columns.' + 1) + $row;');

// $order is designed to get the index of an item in the original array,
// and produce the index that item would have if the items appeared in
// column-major order instead of row-major as they appear now
$array = array_map($order, array_keys($input));

// replace the old keys with the new ones
$array = array_combine($array, $input);

// sort based on the new keys; this will effectively transpose the matrix,
// if it were already structured as a matrix instead of a single-dimensional array
ksort($array);

// done!
$array = array_chunk($array, $columns);
print_r($array);

See it in action.

Answer 5

YAYAYAY!! I've got it. You could turn this into a function if you'll be doing it regularly.

# Here we setup our array and the number of columns we want.
$myArray = range('a','d');  
$numCols = 3;

# Here we break ourselves up into columns
for ($i = 0; $i < $numCols; $i++) {
    $numRows = ceil(count($myArray) / ($numCols - $i));
    $columns[$i] = array_slice($myArray,0,$numRows);
    $myArray = array_slice($myArray,$numRows);
}

# Here we transpose our array to be in rows instead of columns.
for ($i = 0; $i < $numCols; $i++) {
    for ($j = 0; $j < count($columns[$i]); $j++) {
        $rows[$j][$i] = $columns[$i][$j];
    }
}

# Our rows are now in $rows
var_dump($rows);

The output from this is:

array(2) {
  [0]=>
  array(3) {
    [0]=>
    string(1) "a"
    [1]=>
    string(1) "c"
    [2]=>
    string(1) "d"
  }
  [1]=>
  array(1) {
    [0]=>
    string(1) "b"
  }
}

Answer 6

How about:

$arrs = array(
    array('a','b','c'),
    array('a','b','c','d'),
    array('a','b','c','d','e'),
    array('a','b','c','d','e','f'),
    array('a','b','c','d','e','f','g')
);
$nbcols = 3;
foreach ($arrs as $arr) {
    $arr_size = count($arr);
    $nblines = ceil($arr_size/$nbcols);
    $res = array();
    $l = 0;
    foreach ($arr as $el) {
        if ($l == $arr_size - 1 && count($res[0]) < $nbcols) $l=0;
        $res[$l%$nblines][] = $el;
        $l++;
    }
    print_r($res);
}

output:

Array
(
    [0] => Array
        (
            [0] => a
            [1] => b
            [2] => c
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => c
            [2] => d
        )

    [1] => Array
        (
            [0] => b
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => c
            [2] => e
        )

    [1] => Array
        (
            [0] => b
            [1] => d
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => c
            [2] => e
        )

    [1] => Array
        (
            [0] => b
            [1] => d
            [2] => f
        )

)
Array
(
    [0] => Array
        (
            [0] => a
            [1] => d
            [2] => g
        )

    [1] => Array
        (
            [0] => b
            [1] => e
        )

    [2] => Array
        (
            [0] => c
            [1] => f
        )

)

Answer 7

In order to do this, you need to do two operations:

First, split the array into 3 groups, as evenly as possible.

function array_grouped($arr, $group_count)
{
    if (!count($arr)) return array();
    $result = array();
    for ($i = $group_count; $i > 0; --$i)
    {
        # break off the next ceil(remaining count / remaining columns) elements
        # (avoiding FP math, cause that way lies madness)
        $result[] = array_splice($arr, 0, ((count($arr)-1) / $i) + 1);
    }
    return $result;
}

Then, "transpose" the array, so that rows and columns switch places.

function array_transposed($arr)
{
    $result = array();
    foreach ($arr as $x => $subarr)
    {
        foreach ($subarr as $y => $val)
        {
            if (!isset($result[$y])) $result[$y] = array();
            $result[$y][$x] = $val;
        }
    }
    return $result;
}

array_transposed(array_grouped($arr, 3)) gives you entries in the order you want them.

Answer 8

If to say it shortly, then here is a method for that algorithm.

/**
 * @param array $toTransform
 * @param int $columnsMax
 * @return array
 */
private function transformation( array $toTransform, $columnsMax = 3 )
{
    // First divide array as you need
    $listlen   = count( $toTransform );
    $partlen   = floor( $listlen / $columnsMax );
    $partrem   = $listlen % $columnsMax;
    $partition = array();
    $mark      = 0;

    for ( $px = 0; $px < $columnsMax; $px++ )
    {
        $incr             = ( $px < $partrem ) ? $partlen + 1 : $partlen;
        $partition[ $px ] = array_slice( $toTransform, $mark, $incr );
        $mark             += $incr;
    }

    // Secondly fill empty slots for easy template use
    $result = array();

    for ( $i = 0; $i < count( $partition[0] ); $i++ )
    {
        $tmp = array();

        foreach ( $partition as $column )
        {
            if ( isset( $column[ $i ] ) )
            {
                $tmp[] = $column[ $i ];
            }
            else
            {
                $tmp[] = '';
            }
        }

        $result[] = $tmp;
    }

    return $result;
}

Also I included PHPUnit test for that. You can find it at, that link.