PHP - how to distribute items into two arrays base on values - php

Question

I have this array,
Array
(
[0] => Array
(
[id] => 1
[name] => Item 1
[price] => 10
[weight] => 200
)
[1] => Array
(
[id] => 2
[name] => Item 2
[price] => 100
[weight] => 20
)
[2] => Array
(
[id] => 3
[name] => Item 3
[price] => 30
[weight] => 300
)
[3] => Array
(
[id] => 4
[name] => Item 4
[price] => 20
[weight] => 500
)
[4] => Array
(
[id] => 6
[name] => Item 6
[price] => 40
[weight] => 10
)
[5] => Array
(
[id] => 7
[name] => Item 7
[price] => 200
[weight] => 10
)
)
And I want to split it into two, so I get this result,
Array
(
[0] => Array
(
[0] => Array
(
[id] => 1
[name] => Item 1
[price] => 10
[weight] => 200
)
[1] => Array
(
[id] => 3
[name] => Item 3
[price] => 30
[weight] => 300
)
[2] => Array
(
[id] => 7
[name] => Item 7
[price] => 200
[weight] => 10
)
)
[1] => Array
(
[0] => Array
(
[id] => 4
[name] => Item 4
[price] => 20
[weight] => 500
)
[1] => Array
(
[id] => 6
[name] => Item 6
[price] => 40
[weight] => 10
)
[2] => Array
(
[id] => 2
[name] => Item 2
[price] => 100
[weight] => 20
)
)
)
Any ideas?
The tricky of this is that the total price of each package must not be more than 250. while the total weight of each must be as even as possbile (even thought it is impossible). You can see what I mean in this picture,
name weight price
package 1
Item 1 200 10
Item 3 300 30
Item 7 10 200
(total) 510 240
package 2
Item 4 500 20
Item 6 10 40
Item 2 20 100
(total) 530 160
So is it possible to move around the items between these two packages so that total weights are distributed 'evenly'? It seems that it cannot be achieved without 'moving' them manually. I can't think of any way to achieve the goal by automatic programme. Can you?

Answer 1

Sort the array by weight
usort($array, function($a, $b) {return $a['weight']>$b['weight'];});
We init our result tables, with a price and weight counters
$sum=Array(
Array("weight" => 0, "price" => 0, "res" => Array()),
Array("weight" => 0, "price" => 0, "res" => Array()));
Then we loop on array
while ($obj=array_pop($array)) {
We select the lower result array
$ind=($sum[0]['weight']<$sum[1]['weight']) ? 0 : 1;
except if it has reached the max amount
if ($sum[$ind]['price']+$obj['price']>250) {
$ind=1-$ind;
## object will be skipped if it can't fit in the allowed amount
if ($sum[$ind]['price']+$obj['price']>250) continue;
}
and then we fill it
array_push($sum[$ind]['res'], $obj);
$sum[$ind]['weight']+=$obj['weight'];
$sum[$ind]['price']+=$obj['price'];
}
print_r($sum);
Result as expected:
Array
(
[0] => Array
(
[weight] => 510
[price] => 240
[res] => Array
(
[0] => Array
(
[id] => 3
[name] => Item 3
[price] => 30
[weight] => 300
)
[1] => Array
(
[id] => 1
[name] => Item 1
[price] => 10
[weight] => 200
)
[2] => Array
(
[id] => 7
[name] => Item 7
[price] => 200
[weight] => 10
)
)
)
[1] => Array
(
[weight] => 530
[price] => 160
[res] => Array
(
[0] => Array
(
[id] => 4
[name] => Item 4
[price] => 20
[weight] => 500
)
[1] => Array
(
[id] => 2
[name] => Item 2
[price] => 100
[weight] => 20
)
[2] => Array
(
[id] => 6
[name] => Item 6
[price] => 40
[weight] => 10
)
)
)
)

Answer 2

It have nothing to do with PHP or arrays. As I understand your question it's kind of Multiple knapsack problem. So it's lots of math (see some solution here) and maybe easiest way is to programmatically chaeck all possible variants.