/**
* Merge an array of arrays so that the result is in sorted order.
*
* @param array $arrays
* @return array
*/
function mergeSortedArrays(array $arrays)
{
if (empty($arrays)) {
return [];
}
$heads = array_fill(0, count($arrays), 0);
$minHeap = new \SplMinHeap();
$result = [];
// Insert the first value from each sorted array into the min heap
for ($i = 0; $i < count($arrays); $i++) {
if (!empty($arrays[$i])) {
$minHeap->insert([$arrays[$i][0], $i]);
$heads[$i] = 1;
}
}
while (!$minHeap->isEmpty()) {
$smallestArray = $arrays[$minHeap->top()[1]];
$smallestHead = $heads[$minHeap->top()[1]];
$result[] = $minHeap->top()[0];
// If the smallest array has more values, put the next one into the heap
if ($smallestHead < count($smallestArray)) {
$minHeap->insert([$smallestArray[$smallestHead], $minHeap->top()[1]]);
$heads[$minHeap->top()[1]] += 1;
}
$minHeap->extract();
}
return $result;
}
<?php
$h = new SplMinHeap();
try {
$h->top();
} catch (Exception $e) {
echo $e->getMessage();
}
<?php
/**
* A kulcsot nem tartja meg
*/
$data = [2, 4, 1, 76, 42, 23, 0, 10, 2];
$heap = new SplMinHeap();
foreach ($data as $v) {
$heap->insert($v);
}
printf("TOP: %s\n", $heap->top());
foreach ($heap as $k => $v) {
printf("%s => %s\n", $k, $v);
}
$heap = new SplMaxHeap();
foreach ($data as $v) {
$heap->insert($v);
}
printf("TOP: %s\n", $heap->top());
foreach ($heap as $k => $v) {
printf("%s => %s\n", $k, $v);
}
<?php
$h = new SplMinHeap();
$h->insert(5);
// top doesn't take any args, lets see what happens if we give it one
$h->top('bogus');
/**
* Uses the chi-squared feature selection algorithm to rank features by
* informativeness, and return a map from old feature indices to new ones.
*
* @param object $features full feature set
* @return array associative array mapping a subset of the original feature
* indices to new indices
*/
function select(Features $features)
{
$n = $features->numFeatures();
$selected = new SplMinHeap();
$allowed = isset($this->max) ? min($this->max, $n) : $n;
$labels = array(-1, 1);
/*
Start with 1, since 0 is dedicated to the constant intercept term;
<= $n because n is the last feature.
*/
for ($j = 1; $j <= $n; $j++) {
$max_chi2 = 0.0;
foreach ($labels as $label) {
/*
t = term present
l = document has label
n = negation
*/
$stats = $features->varStats($j, $label);
list($t_l, $t_nl, $nt_l, $nt_nl) = $stats;
$num = $t_l * $nt_nl - $t_nl * $nt_l;
$den = ($t_l + $t_nl) * ($nt_l + $nt_nl);
$chi2 = $den != 0 ? $num * $num / $den : INF;
if ($chi2 > $max_chi2) {
$max_chi2 = $chi2;
}
}
/*
Keep track of top features in a heap, as we compute
informativeness.
*/
if ($allowed > 0) {
$selected->insert(array($max_chi2, $j));
$allowed -= 1;
} else {
list($other_chi2, $_) = $selected->top();
if ($max_chi2 > $other_chi2) {
$selected->extract();
$selected->insert(array($max_chi2, $j));
}
}
}
return $this->buildMap($selected);
}
public final function getCoreExtension()
{
return self::$extMinHeap->top();
}
