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PHP Array Exercises : Sort an array of positive integers using the Bead-Sort Algorithm

PHP Array: Exercise-10 with Solution

Write a PHP program to sort an array of positive integers using the Bead-Sort Algorithm.

According to Wikipedia "Bead-sort is a natural sorting algorithm, developed by Joshua J. Arulanandham, Cristian S. Calude and Michael J. Dinneen in 2002. Both digital and analog hardware implementations of bead sort can achieve a sorting time of O(n); however, the implementation of this algorithm tends to be significantly slower in software and can only be used to sort lists of positive integers".

Input array : Array ( [0] => 5 [1] => 3 [2] => 1 [3] => 3 [4] => 8 [5] => 7 [6] => 4 [7] => 1 [8] => 1 [9] => 3 )

Sample Solution:

<?php
function columns($uarr)
{
$n=$uarr;
if (count($n) == 0)
 return array();
else if (count($n) == 1)
 return array_chunk($n[0], 1);
array_unshift($uarr, NULL);
 $transpose = call_user_func_array('array_map', $uarr);
return array_map('array_filter', $transpose);
}
function bead_sort($uarr)
{
foreach ($uarr as $e)
 $poles []= array_fill(0, $e, 1);
return array_map('count', columns(columns($poles)));
}
echo 'Original Array : '.'
';
print_r(array(5,3,1,3,8,7,4,1,1,3));
echo '
'.'After Bead sort : '.'
';
print_r(bead_sort(array(5,3,1,3,8,7,4,1,1,3)));
?>

Sample Output:

Original Array :                                            
Array                                                       
(                                                           
    [0] => 5                                                
    [1] => 3                                                
    [2] => 1                                                
    [3] => 3                                                
    [4] => 8                                                
    [5] => 7                                                
    [6] => 4                                                
    [7] => 1                                                
    [8] => 1                                                
    [9] => 3                                                
)                                                           
                                                            
After Bead sort :                                           
Array                                                       
(                                                            
    [0] => 8                                                
    [1] => 7                                                
    [2] => 5                                                
    [3] => 4                                                
    [4] => 3                                                
    [5] => 3                                                
    [6] => 3                                                
    [7] => 1                                                
    [8] => 1                                                
    [9] => 1                                                
) 

Flowchart:

Flowchart: Sort an array of positive integers using the Bead-Sort Algorithm

PHP Code Editor:

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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