PHP Searching and Sorting Algorithm: Strand sort
PHP Searching and Sorting Algorithm: Exercise-15 with Solution
Write a PHP program to sort a list of elements using Strand sort.
This is a way of sorting numbers by extracting shorter sequences of already sorted numbers from an unsorted list.
Sample Solution :
PHP Code :
<?php
$lst = new SplDoublyLinkedList();
foreach (array(100, 0, 2, 5, -1, 4, 1) as $v)
$lst->push($v);
foreach (strandSort($lst) as $v)
echo "$v ";
echo " ".PHP_EOL;
function strandSort(SplDoublyLinkedList $lst) {
$result = new SplDoublyLinkedList();
while (!$lst->isEmpty()) {
$sorted = new SplDoublyLinkedList();
$remain = new SplDoublyLinkedList();
$sorted->push($lst->shift());
foreach ($lst as $item) {
if ($sorted->top() <= $item) {
$sorted->push($item);
} else {
$remain->push($item);
}
}
$result = _merge($sorted, $result);
$lst = $remain;
}
return $result;
}
function _merge(SplDoublyLinkedList $left, SplDoublyLinkedList $right) {
$res = new SplDoublyLinkedList();
while (!$left->isEmpty() && !$right->isEmpty()) {
if ($left->bottom() <= $right->bottom()) {
$res->push($left->shift());
} else {
$res->push($right->shift());
}
}
foreach ($left as $v) $res->push($v);
foreach ($right as $v) $res->push($v);
return $res;
}
?>
Sample Output:
-1 0 1 2 4 5 100
Flowchart :
PHP Code Editor:
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Previous: Write a PHP program to sort a list of elements using Bogo sort.
Next: Write a PHP program to sort a list of elements using Patience sort.
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PHP: Tips of the Day
How to Sort Multi-dimensional Array by Value?
Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:
Example:
function sortByOrder($a, $b) { return $a['order'] - $b['order']; } usort($myArray, 'sortByOrder');
Starting in PHP 5.3, you can use an anonymous function:
usort($myArray, function($a, $b) { return $a['order'] - $b['order']; });
And finally with PHP 7 you can use the spaceship operator:
usort($myArray, function($a, $b) { return $a['order'] <=> $b['order']; });
To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.
usort($myArray, function($a, $b) { $retval = $a['order'] <=> $b['order']; if ($retval == 0) { $retval = $a['suborder'] <=> $b['suborder']; if ($retval == 0) { $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder']; } } return $retval; });
If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual
Ref : https://bit.ly/3i77vCC
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