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PHP Searching and Sorting Algorithm: Cocktail sort

PHP Searching and Sorting Algorithm: Exercise-7 with Solution

Write a PHP program to sort a list of elements using Cocktail sort.

Cocktail shaker sort (also known as bidirectional bubble sort, cocktail sort, shaker sort, ripple sort, shuffle sort, or shuttle sort ) is a variation of bubble sort that is both a stable sorting algorithm and a comparison sort. The algorithm differs from a bubble sort in that it sorts in both directions on each pass through the list. This sorting algorithm is only marginally more difficult to implement than a bubble sort and solves the problem of turtles in bubble sorts. It provides only marginal performance improvements, and does not improve asymptotic performance; like the bubble sort, it is not of practical interest, though it finds some use in education.

Visualization of shaker sort :

Sorting shaker sort animation

Sample Solution :

PHP Code :

<?php
function cocktailSort($my_array)
 {
	if (is_string($my_array))
	$my_array = str_split(preg_replace('/\s+/','',$my_array));
 
	do{
		$swapped = false;
		for($i=0;$i<count($my_array);$i++){
			if(isset($my_array[$i+1])){
				if($my_array[$i] > $my_array[$i+1]){
					list($my_array[$i], $my_array[$i+1]) = array($my_array[$i+1], $my_array[$i]);
					$swapped = true;
				}
			}			
		}
 
		if ($swapped == false) break;
 
		$swapped = false;
		for($i=count($my_array)-1;$i>=0;$i--){
			if(isset($my_array[$i-1])){
				if($my_array[$i] < $my_array[$i-1]) {
					list($my_array[$i],$my_array[$i-1]) = array($my_array[$i-1],$my_array[$i]);
					$swapped = true;
				}
			}
		}
	}while($swapped);
 
	return $my_array;
}
$test_array = array(3, 0, 2, 5, -1, 4, 1);
echo "Original Array :\n";
echo implode(', ',$test_array );
echo "\nSorted Array\n:";
echo implode(', ',cocktailSort($test_array)). PHP_EOL;
?>

Sample Output:

3, 0, 2, 5, -1, 4, 1                                                
Sorted Array :                                                      
-1, 0, 1, 2, 3, 4, 5

Flowchart :

Flowchart: PHP - program of Cocktail sort

PHP Code Editor:


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Previous: Write a PHP program to sort a list of elements using Bubble sort.
Next: Write a PHP program to sort a list of elements using Comb sort.

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PHP: Tips of the Day

PHP: ?: operator (the 'Elvis operator') in PHP

It evaluates to the left operand if the left operand is truthy, and the right operand otherwise.

In pseudocode,

foo = bar ?: baz;

roughly resolves to

foo = bar ? bar : baz;

or

if (bar) {
    foo = bar;
} else {
    foo = baz;
}

with the difference that bar will only be evaluated once.

You can also use this to do a "self-check" of foo as demonstrated in the code example you posted:

foo = foo ?: bar;

This will assign bar to foo if foo is null or falsey, else it will leave foo unchanged.

Some more examples:

<?php
    var_dump(5 ?: 0); // 5
    var_dump(false ?: 0); // 0
    var_dump(null ?: 'foo'); // 'foo'
    var_dump(true ?: 123); // true
    var_dump('rock' ?: 'roll'); // 'rock'
?>

By the way, it's called the Elvis operator.

Ref : https://bit.ly/2SYEI83