Finding the Subsets of an Array in PHP

Finding the subsets of an array in PHP

You wish for the power set of $attributes? That is what your question implies.

An example can be found here (quoted for completeness)

<?php 
/** 
* Returns the power set of a one dimensional array, a 2-D array. 
* [a,b,c] -> [ [a], [b], [c], [a, b], [a, c], [b, c], [a, b, c] ]
*/ 
function powerSet($in,$minLength = 1) { 
   $count = count($in); 
   $members = pow(2,$count); 
   $return = array(); 
   for ($i = 0; $i < $members; $i++) { 
      $b = sprintf("%0".$count."b",$i); 
      $out = array(); 
      for ($j = 0; $j < $count; $j++) { 
         if ($b{$j} == '1') $out[] = $in[$j]; 
      } 
      if (count($out) >= $minLength) { 
         $return[] = $out; 
      } 
   } 
   return $return; 
} 

Get subset of array based on values in PHP

You can use array_filter to filter an array down to only the elements you're looking for. Set $subset to whatever value you're searching for, and it'll return the matching elements, without changing the keys.

$subset = 2;

$results = array_filter($array, function ($item) use ($subset) {
    return $item === $subset;
});

print_r($results);

Array
(
[3] => 2
[4] => 2
)

See https://eval.in/926983

how to find possible subsets of a given array?

The table is entirely unnecessary.

One idea is to imagine a bit wise representation of each weekday, whereby:

Monday = 1
Tuesday = 2
Wednesday = 4
Thursday = 8
Etc

Every combination of days can then be represented by a single number from 1 to 127.

See Working with bitcode for a fuller explanation

How to find sum of each subset in php?

The $result in the function is array of arrays so you cannot just use array_sum on it. In order to sum each of the sub-set you need to use array_map together with array_sum.

You can do it in the end of the function - just add print_r(array_map("array_sum", $results)); as last line (if you want it as output).

I liked @splash58 comment about using it outside the function with:

$ans = array_map("array_sum", powerSet($array));

Get a subset of an array based on an array of keys

array_diff_key and array_intersect_key are probably what you want.

Create subset of array in php

See array_chunk function.

To example:

$input_array = array('a', 'b', 'c', 'd', 'e');
print_r(array_chunk($input_array, 2));

Result:

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

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

    [2] => Array
        (
            [0] => e
        )

)

Find all possible unique combinations of elements of an array in PHP

Fast solution using recursion, probably not the best way to do it, but it gets the job done.

<?php

$arr = array(1,2,3);
$result = array();

function combinations($arr, $level, &$result, $curr=array()) {
    for($i = 0; $i < count($arr); $i++) {
        $new = array_merge($curr, array($arr[$i]));
        if($level == 1) {
            sort($new);
            if (!in_array($new, $result)) {
                $result[] = $new;          
            }
        } else {
            combinations($arr, $level - 1, $result, $new);
        }
    }
}
for ($i = 0; $i<count($arr); $i++) {
    combinations($arr, $i+1, $result);
}

// TEST
foreach ($result as $arr) {
    echo join(" ", $arr) . '<br>';
}

?>

Find qualifying subsets and return value that immediately follows

I reckon it is simpler to read your data as a string instead of iterating elements in their current array form.

Just use a lookbehind pattern and match the next occurring integer.

Code: (Demo) (technically better accuracy)

$haystack = [0,0,0,1,1,0,1,1,0,0,1,1,0,0,1];
$needle = [1,1,0];

$regex = sprintf(
    '/(?<=%s,)\d+/',
    implode(',', $needle)
);

var_export(
    preg_match_all($regex, implode(',', $haystack), $m)
    ? $m[0]
    : []
);

Output:

array (
  0 => '1',
  1 => '0',
  2 => '0',
)

---

Or an approach that processes the data in array form, can make iterated calls of array_slice() to achieve the same result. (Demo)

$needleCount = count($needle);
$result = [];
foreach ($haystack as $i => $straw) {
    $start = $i - $needleCount;
    if (
        $start >= 0
        && $needle === array_slice($haystack, $start, $needleCount)
    ) {
        $result[] = $straw;
    }
}

---

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