Anonymous user
Knuth's algorithm S: Difference between revisions
added php
(added php) |
|||
Line 310:
<pre> 30051 29899 30249 30058 30012 29836 29998 29882 30148 29867</pre>
=={{header|PHP}}==
{{works with|PHP|5.3+}}
<lang php><?php
function s_of_n_creator($n) {
$sample = array();
$i = 0;
return function($item) use (&$sample, &$i, $n) {
$i++;
if ($i <= $n) {
# Keep first n items
$sample[] = $item;
} else if (rand(0, $i-1) < $n) {
# Keep item
$sample[rand(0, $n-1)] = $item;
}
return $sample;
};
}
$items = range(0, 9);
echo "Single run samples for n = 3:\n";
$s_of_n = s_of_n_creator(3);
foreach ($items as $item) {
$sample = $s_of_n($item);
echo " Item: $item -> sample: ", implode(', ', $sample), "\n";
}
for ($trial = 0; $trial < 100000; $trial++) {
$s_of_n = s_of_n_creator(3);
foreach ($items as $item)
$sample = $s_of_n($item);
foreach ($sample as $s)
$bin[$s]++;
}
echo "\nTest item frequencies for 100000 runs:\n";
print_r($bin);
?></lang>
;Sample output:
<pre>Single run samples for n = 3:
Item: 0 -> sample: 0
Item: 1 -> sample: 0, 1
Item: 2 -> sample: 0, 1, 2
Item: 3 -> sample: 0, 3, 2
Item: 4 -> sample: 0, 3, 2
Item: 5 -> sample: 0, 3, 2
Item: 6 -> sample: 0, 3, 2
Item: 7 -> sample: 0, 3, 2
Item: 8 -> sample: 0, 3, 2
Item: 9 -> sample: 0, 3, 2
Test item frequencies for 100000 runs:
Array
(
[3] => 30158
[8] => 29859
[9] => 29984
[6] => 29937
[7] => 30361
[4] => 29994
[5] => 29849
[0] => 29724
[1] => 29997
[2] => 30137
)</pre>
=={{header|PicoLisp}}==
| |||