Add restriction to a Knapsack algorithm in php

Question

I need something like this: Algorithm to select Player with max points but with a given cost

I understand the concept of knapsack and I already made an algorithm that gives me the optimal solution using the 0/1 grid system. The problem is that i'm not figuring out how to implement the restrictions and by restrictions I mean only X players for each position. I do not quite understand the answer given by amit in the link above. If you could give me some enlightenment it would be awesome.

Thanks in advance and sorry for my english.

EDIT: Sorry for the lack of information. This is my first question :)

Here is what I've done so far.

$all_players = array();

foreach ($arr_players as $value) {

    $all_players[] = array( "name" => $value['name'],
                            "position" => $value['position'],
                            "salary" => $value['salary'],
                            "score" => $value['score']
                            );

}  //  array sorted by salary


$total_players = count($all_players);
$salary_cap = 601;

//  using the knapsack 0/1 grid method
for ($x = 0; $x < $total_players; $x++) {
    for ($y = 1; $y < $salary_cap; $y++) {
        if ($x == 0) {

            $score_arr[$x][$y] = 0;
            $keep_arr[$x][$y] = 0;

        } else {

            if ($all_players[$x]['salary'] <= $y) {

                $arr_pos = $x - 1;
                $salary_left = $y - $all_players[$x]['salary'];

                if ($all_players[$x]['salary'] == $y) {
                    $score_pres = $all_players[$x]['score'];
                } else {
                    $score_pres = $all_players[$x]['score'] + $score_arr[$arr_pos][$salary_left];
                }

                $score_prev = $score_arr[$arr_pos][$y];

                if ($score_pres > $score_prev) {
                    $score_arr[$x][$y] = $score_pres;
                    $keep_arr[$x][$y] = 1;
                } else {
                    $score_arr[$x][$y] = $score_prev;
                    $keep_arr[$x][$y] = 0;
                }

            } else {

                $score_arr[$x][$y] = 0;
                $keep_arr[$x][$y] = 0;

            }
        }
    }
}


$total_players = $total_players - 1;
$salary_left = 600;
$best_lineup = array();

//
for ($x = $total_players; $x > -1; $x--) {
    if ($keep_arr[$x][$salary_left] == 1) {

        $best_lineup[] = $all_players[$x]['name'];
        $salary_left = $salary_left - $all_players[$x]['salary'];

    }
}

/////////////////////////////////////////////////
/*
The output:

Array
(
    [0] => Ramon Sessions  //  PG
    [1] => Omri Casspi  //  SF
    [2] => D.J. Augustin  //  PG
    [3] => Steven Adams  //  C
    [4] => Zach LaVine  //  PG
    [5] => Kris Humphries  //  PF
    [6] => Isaiah Canaan  //  PG
    [7] => Corey Brewer  //  SF
    [8] => Rodney Stuckey  //  SG
    [9] => O.J. Mayo  //  SG
    [10] => Greg Monroe  //  PF
    [11] => DeMarcus Cousins  //  C
)
*/

Now I need to restrict this array to have only 2 players from each position (PG, SG, SF, PF) and 1 from C position for the best 9 player lineup.

Answer 1

//  team position with wanted amount of players
$team = array("PG" => 2, "SG"  => 2, "SF"  => 2, "PF"  => 2, "C"  => 1);

$x = $total_players;
$salary_left = 600;
$best_lineup = array();

//
while (--$x >  -1) {
    if ($keep_arr[$x][$salary_left] == 1) {

        $pos = $all_players[$x]['position'];
        if ($team[$pos] > 0) {
            //  we need another player for that pos
            $team[$pos]--; // same as $team[$pos] = $team[$pos] -1;

            $best_lineup[] = $all_players[$x]['name'];
            $salary_left = $salary_left - $all_players[$x]['salary'];
        }
    }
}