/**
* 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
$pq = new SplMinHeap();
$pq->insert(array(3, 'Clear drains'));
$pq->insert(array(4, 'Feed cat'));
$pq->insert(array(5, 'Make tea'));
$pq->insert(array(1, 'Solve RC tasks'));
$pq->insert(array(2, 'Tax return'));
while (!$pq->isEmpty()) {
print_r($pq->extract());
}
