<?php
$facts = [];
function fact($N, &$facts)
{
if ($N<=1) {
return 1;
}
if (!array_key_exists($N, $facts)) {
$facts[$N] = $N * fact($N - 1, $facts);
}
return $facts[$N];
}
function C($n, $k, &$facts)
{
return fact($n, $facts) / fact($k, $facts) / fact($n - $k, $facts);
}
function combination ($index, $k, $A, $facts)
{
$res = [0];
$n = sizeof($A);
$s = 0;
for ($t = 1; $t <= $k; $t++) {
$j = $res[$t - 1] + 1;
while (($j < ($n - $k + $t)) && (($s + C($n - $j, $k - $t, $facts)) <= $index)) {
$s += C($n - $j, $k - $t, $facts);
$j++;
}
$res[] = $j;
}
array_splice($res, 0, 1);
print_r($res);
}
$m = [1,2,3,4,5];
for ($i = 0; $i < C(sizeof($m), 3, $facts); $i++) {
combination($i, 3, array_slice($m, 0), $facts);
}
preferences:
52.58 ms | 402 KiB | 5 Q