PHP排序數組的平均數

Question

我有一個整數值的數組（超過4個鍵）。我必須選擇4個不同的值，以便這些數字的平均值等於給定的值，如果不可能，則爲假。 做什麼是最好的方法？ （算法）

Answer 1

我將如何完成它是找到所有的給定長度的陣列的可能的子集，然後依次通過他們，並計算它們的平均值：

function get_subset_with_average($average, Array $data, $length) { 
    // Make sure we can calculate the subsets 
    if (count($data) < $length) { 
     throw new Exception("The subset length is more than the size of the array"); 
    } 
    $a = $b = 0; 
    $subset = []; 
    $subsets = []; 

    // Loop through the data and get all subset combinations 
    while ($a < count($data)) { 
     $current = $data[$a++]; 
     $subset[] = $current; 
     if (count($subset) == $length) { 
      $subsets[] = $subset; 
      array_pop($subset); 
     } 
     if ($a == count($data)) { 
      $a = ++$b; 
      $subset = []; 
     } 
    } 

    // Loop through the subsets and check if the average equals the desired average 
    foreach ($subsets as $set) { 
     if (array_sum($set)/count($set) == $average) { 
      return $set; 
     } 
    } 
    return false; 
} 
$data = array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15); 

var_dump(get_subset_with_average(2.5, $data, 4)); 
var_dump(get_subset_with_average(5.75, $data, 4)); 
var_dump(get_subset_with_average(9.3, $data, 4)); 
var_dump(get_subset_with_average(13, $data, 4)); 

這將輸出：

array(4) { 
    [0]=> 
    int(1) 
    [1]=> 
    int(2) 
    [2]=> 
    int(3) 
    [3]=> 
    int(4) 
} 
array(4) { 
    [0]=> 
    int(2) 
    [1]=> 
    int(3) 
    [2]=> 
    int(4) 
    [3]=> 
    int(14) 
} 
bool(false) 
bool(false)