Combinação de faturas

combina_faturas.php

<?php
function permutations($pool, $r = null) {
    $n = count($pool);

    if ($r == null) {
        $r = $n;
    }

    if ($r > $n) {
        return;
    }

    $indices = range(0, $n - 1);
    $cycles = range($n, $n - $r + 1, -1); // count down

    yield array_slice($pool, 0, $r);

    if ($n <= 0) {
        return;
    }

    while (true) {
        $exit_early = false;
        for ($i = $r;$i--;$i >= 0) {
            $cycles[$i]-= 1;
            if ($cycles[$i] == 0) {
                // Push whatever is at index $i to the end, move everything back
                if ($i < count($indices)) {
                    $removed = array_splice($indices, $i, 1);
                    array_push($indices, $removed[0]);
                }
                $cycles[$i] = $n - $i;
            } else {
                $j = $cycles[$i];
                // Swap indices $i & -$j.
                $i_val = $indices[$i];
                $neg_j_val = $indices[count($indices) - $j];
                $indices[$i] = $neg_j_val;
                $indices[count($indices) - $j] = $i_val;
                $result = [];
                $counter = 0;
                foreach ($indices as $indx) {
                    array_push($result, $pool[$indx]);
                    $counter++;
                    if ($counter == $r) break;
                }
                yield $result;
                $exit_early = true;
                break;
            }
        }
        if (!$exit_early) {
            break; // Outer while loop
        }
    }
}

$faturas=array(100,12.3,54.2,20,49.2,90.54,64);
$test_cases=array();
for($i=1;$i<count($faturas);$i++){
array_push($test_cases,array($i))  ;
}
array_push($test_cases,$faturas);
for($i=2;$i<count($faturas);$i++){  
  $perm=iterator_to_array(permutations($faturas,$i));
  foreach($perm as $row){
    array_push($test_cases,$row);
  }
}
foreach($test_cases as $row){
    print implode(", ", $row) . "\n";
}