MobKool Blog » Algorithms

PHP Insertion Sort

JFP — Wed, 10 Feb 2010 20:38:45 +0000

Insertion sorts are good when your data is already partially sorted, or if you have a small collection to sort. That’s about the best I can say for them. Here’s two versions in PHP. The first uses two functions:
function insertion_sort($a) { for ($i=1; $i < count($a); $i++) { inserter(&$a,$i,$a[$i]); } }
function inserter($a,$pos,$a_value) { $temp = $a[$pos]; $i = $pos; while($i >= 0 && $a[$i-1] > $a_value) { $a[$i] = $a[$i-1]; $i = $i-1; } $a[$i] = $temp; }

The second uses one function:

function insertion_sort($a) { for($j=1; $j < count($a); $j++) { $temp = $a[$j]; $i = $j; while(($i >= 0) && ($a[$i-1] > $temp)){ $a[$i] = $a[$i-1]; $i--; } $a[$i] = $temp; } }

To test them, use the following code:

$haystack = array(1,5,6,3); insertion_sort(&$haystack); print_r ($haystack);

PHP Sequential or Linear Search Algorithm

JFP — Mon, 08 Feb 2010 22:07:04 +0000

Sequential search, or linear search, is the simplest searching algorithm. Indeed, given it’s brute force approach of just traversing a collection from the first to last element, it’s hard to justify calling it an algorithm at all. However, here’s an example in PHP:
function sequential_search($needle,$haystack) { for($i = 0; $i < count($haystack); $i++) { if ($needle == $i) return true; } return false; }

Here's an example of how you would use this algorithm to look for the number 3 inside an array:

$haystack = array(1,2,3,4); $needle = 3; $success = sequential_search($needle, $haystack);

PHP Bubble Sort

JFP — Mon, 31 Dec 2007 04:02:22 +0000

One of an occasional series of posts on PHP algorithms. I found this originally at United Scripters, and bookmarked it for some reason.

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