parse matrix and mapped math-function in array in PHP

Question

I have a given array, built like this:

[[0,2,0,1], 0,5,0,0], 1,0,1,3]]

(for the readability)

array(3) { [0]=> array(4) { [0] => int(0) [1] => int(2) [2] => int(0) [3] => int(1) } [1]=> array(4) { [0] => int(0) [1] => int(5) [2] => int(0) [3] => int(0) } [2]=> array(4) { [0] => int(1) [1] => int(0) [2] => int(1) [3] => int(3) } }

This input can vary as you can imagine, in length and heights and numbers, but not in the semantic.

I'd like to "map" a simple function, which does some basic math, which should calculate as follows:

If there are 0's in the the columnn, ignore all further values (values before are still added). Otherwise add all values to a sum.

in my example above, I have to add:

2 + 5 + 1

the 1st row has 0's in the first 2 lines, so we don't add the 1.
2nd row has 2 + 5 (7), the 0 afterwards doesn't matter
3rd row same as 1st one
4th row only adds 1 (before the 0, the 3 afterwards is ignored).

I tried to iterate through the given matrix with nested foreach-statements like this:

foreach($matrix as $k => $v) { // $v = 0,1,1,2 ... foreach($v as $lineValues) { var_dump($lineValues); } }

This gives me an output of:

int(0) int(1) int(1) int(2) int(0) int(5) int(0) int(0) int(2) int(0) int(3) int(3)

I thought about counting the elements in each row and divide this result afterwards to rebuild the array and to compare if there are 0's or not. If there is a 0, all further additions wouldn't be important, so I'd jump to the 2nd values with incrementing $j ...

$lineValues][$i][$j] // (1st row, 1st value) $lineValues][$i+1][$j] // (2nd row, 1st value) ...

That didn't help me that much. I also tried to explode each line to build an easier-to-read array with explode("],", $v), but that didn't do the trick either.

Keeping all this in the back of my head, I thought about mapping a function to this, but this is where I'm stuck. I guess (correct me if I'm wrong), that such a function should be the wisest choice, when it comes down to performance?

Is there ever a time where a # in the matrice will be greater than 9? — thecoolestguyever123
– thecoolestguyever123, Commented Dec 4, 2018 at 12:42
Is input of type string or array? You said string and then later stated it's an array. If it is an array then given input should cause a syntax error. Please provide the right input and its type. — revo
– revo, Commented Dec 4, 2018 at 12:47
My bad, @revo. The param / input is of the type "array". I'll correct that right now — Saffe
– Saffe, Commented Dec 4, 2018 at 12:49
Couldn't you just remove the brackets & explode by , then iterate over it? You know that every 4th # is in the same column. — thecoolestguyever123
– thecoolestguyever123, Commented Dec 4, 2018 at 12:52

Jules R · Accepted Answer · 2018-12-04 13:01:38Z

There are possibly cleverer ways to do it, but it works.

function parse($matrix) { $sum = 0; $sum_detail = array(); $lineLength = count($matrix[0]); for($i = 0; $i < $lineLength; $i++) { foreach($matrix as $line) { if($line[$i] == 0) break; else $sum += $line[$i]; } } echo $sum; }

The idea is to sum first element for line #1, #2, #3 ..., then second element, then third, etc. Working demo here

revo · Accepted Answer · 2018-12-04 13:42:34Z

You could iterate over each element and blacklist its column id if the element is 0.

PHP code (See live demo here):

foreach ($rows as $row) { foreach ($row as $columnId => $columnValue) { if ($columnValue == 0) { $blackListedColumns[] = $columnId; continue; } if (!in_array($columnId, $blackListedColumns)) { $entries[] = $columnValue; } } } print_r($entries);

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