Combine multiple arrays - php

Question

I have arrays like this
Array 1:
Array
(
[0] => Array
(
[0] => 0
[1] => -0.025
)
[1] => Array
(
[0] => 0
[1] => -0.025
)
[2] => Array
(
[0] => 0
[1] => -0.025
)
)
Array 2:
Array
(
[0] => Array
(
[0] => 0
[1] => -0.025
)
[1] => Array
(
[0] => 0
[1] => -0.025
)
)
Array 3:
Array
(
[0] => Array
(
[0] => 0
[1] => -0.025
)
[1] => Array
(
[0] => 0
[1] => -0.025
)
[2] => Array
(
[0] => 0
[1] => -0.025
)
[3] => Array
(
[0] => 0
[1] => -0.025
)
)
and more of them.
I want to combine them to this
Array
(
[0] => Array
(
[0] => 0
[1] => -0.025
[2] => 0
[3] => -0.025
[4] => 0
[5] => -0.025
)
[1] => Array
(
[0] => 0
[1] => -0.025
[2] => 0
[3] => -0.025
[4] => 0
[5] => -0.025
)
[2] => Array
(
[0] => 0
[1] => -0.025
[2] => 0
[3] => 0
[4] => 0
[5] => -0.025
)
[3] => Array
(
[0] => 0
[1] => 0
[2] => 0 // These (0-3) are 0 because the other two arrays haven't 3 in the first level
[3] => 0
[4] => 0
[5] => -0.025
)
)
The arrays have a different number of entries in the first level. In the second level there are always 2 entries.
In the second level of the combined array the first two keys (0 and 1) should always have the entries from the first array. The second two keys (2 and 3) should always have the entries from the second array and so on. In my example there are 30 arrays that I want to combine.
If an array does have more first level entries than others all entries should have 0 as value.
I hope you understand this :)

Answer 1

I built it ;-/
Working demonstration at eval.in
Requirements:
Basically it is transposing rows into columns.
the output columns all have the length of the longest array.
The source arrays can have different lengths. Any empty entries are assumed to have a value of array(0, 0).
The output columns are converted into a single dimensional array. i.e. source value arrays are appended to the column array.
Explanation:
I decided to use the internal iterator that all arrays have. i.e. the arrays already can record there own state such as current position (row) that they are on.
After that it is just 'housekeeping':
keep a list of which arrays still have entries to be processed. When none of them have then we are finished.
record which output column ($mergedEntryNo) that we are creating.
scan along each (row) reading entries for the current row.
after each row: advance to the next row and record which arrays are active - if any.
The class (SimpleMerge) that does the work
class SimpleMerge {
protected $sources = array(); // a list of arrays!
protected $sourceCount = 0; // useful
protected $isActive = array(); // which of them have entries to process.
public $merged = array(); // output in here and public
protected $anyActiveSources = false;
// need a list of arrays
public function __construct(array $allSources)
{
$this->sources = $allSources;
$this->sourceCount = count($allSources);
$this->isActive = array_fill(0, $this->sourceCount, true);
}
// generate the output by scanning the arrays line by line
public function generateOutput()
{
$this->generateInit();
$mergedEntryNo = 0;
while ($this->anyActiveSources) {
// set the next output entries
for ($sourceNo = 0; $sourceNo < $this->sourceCount; $sourceNo++) {
$this->addEntry($mergedEntryNo, $this->getEntry($sourceNo));
}
$mergedEntryNo++;
$this->nextPassAdvance();
$this->setIsActiveSource();
}
return $this->merged;
}
// ensure everything is initialized correctly
public function generateInit()
{
$this->merged = array();
foreach ($this->sources as &$source) {
reset($source); // force internal iterators to the start
$this->merged[] = array(); // empty arrays in the output
}
unset($source);
$this->setIsActiveSource();
}
// add to output
public function addEntry($mergedNo, array $values)
{
foreach ($values as $value) {
$this->merged[$mergedNo][] = $value;
}
}
// get the current source entry - will be array of zeroes if end of array
public function getEntry($sourceNo)
{
if ($this->isActive[$sourceNo]) {
return current($this->sources[$sourceNo]);
}
else {
return array(0, 0);
}
}
// check and set which ones are still active and also indicate if any are active
public function setIsActiveSource()
{
$activeCount = 0;
for ($sourceNo = 0; $sourceNo < $this->sourceCount; $sourceNo++) {
$isActive = current($this->sources[$sourceNo]) !== false;
$this->isActive[$sourceNo] = $isActive;
$activeCount = $activeCount + ($isActive ? 1 : 0);
}
$this->anyActiveSources = $activeCount > 0;
}
// advance iterators on the sources that are still active
public function nextPassAdvance()
{
for ($sourceNo = 0; $sourceNo < $this->sourceCount; $sourceNo++) {
if ($this->isActive[$sourceNo]) { // was last time
next($this->sources[$sourceNo]);
}
}
}
}
Run it
// create and run the generator...
$mergeAll = new SimpleMerge($allSourcesList);
$merged = $mergeAll->generateOutput();
Output:
Note, there are no zero values in the input. The values indicate source table and entry number.
Outpt: Array
(
[0] => Array
(
[0] => 11
[1] => -11.025
[2] => 21
[3] => -21.025
[4] => 31
[5] => -31.025
[6] => 41
[7] => -41.025
)
[1] => Array
(
[0] => 12
[1] => -12.025
[2] => 22
[3] => -22.025
[4] => 32
[5] => -32.025
[6] => 42
[7] => -42.025
)
[2] => Array
(
[0] => 13
[1] => -13.025
[2] => 0
[3] => 0
[4] => 33
[5] => -33.025
[6] => 43
[7] => -43.025
)
[3] => Array
(
[0] => 0
[1] => 0
[2] => 0
[3] => 0
[4] => 34
[5] => -34.025
[6] => 44
[7] => -44.025
)
)