在数组中搜索唯一元素的算法？

Question

使用哪种算法搜索数组中的唯一元素？

例如数组是：

$arr = [ 
    ["date" => "2015/04/05", 
    "country" => "UK", 
    "number" => 3], 

    ["date" => "2015/04/05", 
    "country" => "UK", 
    "number" => 3], 

    ["date" => "2015/04/05", 
    "country" => "UK", 
    "number" => 3], 

    ["date" => "2015/04/05", 
    "country" => "UK", 
    "number" => 4], 

]; 

所以，我需要算多少具有独特number元素？

在结果，我应该得到以下结构：

["UK" => array("total" => "2")] 

凡total是在阵列的独特number数。

我试着为：

$output = []; 

foreach ($arr as $k => $value) { 

      $output[ 
       $value[ 
        "country" 
       ]][$value["date"]][$value["number"] 
      ] = true; 
     } 

     foreach ($output as $k => $v) { 

      foreach ($v as $c => $t) { 

       $arr[$k][$c] = count($t); 
      } 
     } 

但这个代码看起来那么可怕，随着循环。此外，我认为有一个微不足道的算法来解决这些问题。

Answer 1

$arr = [ 
    ["date" => "2015/04/05", "country" => "UK", "number" => 3], 
    ["date" => "2015/04/05", "country" => "UK", "number" => 3], 
    ["date" => "2015/04/05", "country" => "UK", "number" => 3], 
    ["date" => "2015/04/05", "country" => "UK", "number" => 4], 
]; 

$result=array(); 
foreach($arr as $value) 
{ 
    $result[$value["country"]][$value['number']] = 1; 
} 

foreach ($result as $country => $a) { 
    $answer[$country]['total'] = count($a); 
} 

print_r($answer); 

结果：

Array 
(
    [UK] => Array 
     (
      [total] => 2 
     ) 

) 

Answer 2

试试这个希望这会帮助你。这里我们使用foreacharray_unique和array_map来实现所需的输出。

Try this code snippet here

$result = array(); 
foreach ($arr as $value) 
{ 
    $result[$value["country"]][] = $value["number"]; 
} 
$result = array_map(function($value){ 
    return array("total"=>count(array_unique($value))); 
}, $result); 
print_r($result) 

Answer 3

像这样的东西会给你所需的输出。

$array = []; 

foreach (array_unique(array_column($arr, 'country')) as $country) { 
    $filter = array_filter($arr, function ($obj) use ($country) { 
      return $obj['country'] == $country; 
    }); 
    $array[$country] = array("total" => count(array_unique(array_column($filter, 'number')))); 
} 

print_r($array);