Weighted array based on user input

Question

I am attempting to allow a user to create an array of index's which are then added to an array with a percentage associated with it. Here is an example:

EX1

$pages[] = array('index1.php','25');
$pages[] = array('index2.php','25');
$pages[] = array('index3.php','50');

or

EX2

$pages[] = array('index1.php','25');
$pages[] = array('index2.php','75');

or even

EX3

$pages[] = array('index1.php','25');
$pages[] = array('index2.php','25');
$pages[] = array('index3.php','25');
$pages[] = array('index4.php','25');

I would like to then create a file with the following contents:

OUTPUT EX1

index1.php
index2.php
index3.php
index3.php

OUTPUT EX2

index1.php
index2.php
index2.php
index2.php

OUTPUT EX3

index1.php
index2.php
index3.php
index4.php

Would I just take the sum of $page[][1] and divide by the number of items in the array?

How does the algorithm know that you want 4 items in the output? — hobbs
– hobbs, Commented Aug 26, 2014 at 23:48

Kevin · Accepted Answer · 2014-08-26 23:47:00Z

2

Just get the minimum number, then just divide it by that, then use str_repeat. (I don't know what's the better way.). Sample Code:

$pages[] = array('index1.php','25');
$pages[] = array('index2.php','25');
$pages[] = array('index3.php','25');
$pages[] = array('index4.php','25');

$min = min(array_map(function($weight){
    return $weight[1];
}, $pages));

foreach($pages as $page) {
    echo str_repeat($page[0] . '<br/>', $page[1] / $min);
}

answered Aug 26, 2014 at 23:47

Kevin

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1 Comment

Kevin Over a year ago

@HydraIO if you want to just put it in a file. just use file_put_contents (with permission of course)

scrowler · Accepted Answer · 2014-08-26 23:46:28Z

2

If you don't mind redundancy, just list the file the number of times given by the weight. For example, you would list index1.php (25/25) times (1), and index3.php (50/25) times (2).

edited Aug 26, 2014 at 23:46

scrowler

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answered Aug 26, 2014 at 23:42

Rob Cozzens

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Comments

Greenonion · Accepted Answer · 2014-08-27 00:08:51Z

Actually i will not agree with answer, let's say you have

$pages[] = array('index1.php','10');
$pages[] = array('index2.php','20');
$pages[] = array('index3.php','40');
$pages[] = array('index4.php','35');

Then your output will be:

index1.php
index2.php
index2.php
index3.php
index3.php
index3.php
index3.php
index4.php
index4.php
index4.php

And this output is wrong. As you see we have index4 three times here.

To compute correct values you should use greatest common divisor. For example:

/*
* function gcd()
* 
* returns greatest common divisor
* between two numbers
* tested against gmp_gcd()
*/
function gcd($a, $b)
{
    if ($a == 0 || $b == 0)
        return abs( max(abs($a), abs($b)) );

    $r = $a % $b;
    return ($r != 0) ?
        gcd($b, $r) :
        abs($b);
}

/*
* function gcd_array()
* 
* gets greatest common divisor among
* an array of numbers
*/
function gcd_array($array, $a = 0)
{
    $b = array_pop($array);
    return ($b === null) ?
        (int)$a :
        gcd_array($array, gcd($a, $b));
}

$array = [10,20,40,35];
$result = gcd_array($array);

for ($i = 0; $i < sizeof($array); $i++)
{
  echo $array[$i] / $result;
  echo "\r\n";
}

In this case output will be:

2 4 8 7

(index1 - 2 times, index2 - 4 times, index 3 - 8 times, index4 - 7 times)

and on my opinion this is correct.

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