doufen3786
doufen3786
2018-10-01 03:12

比较两个多维数组并根据匹配键替换值

已采纳

I have 2 arrays of different length:

$array1 = Array
(
    [0] => Array
        (
            ['_id'] => "Group1"
            ['M'] => 0
            ['F'] => 0
        )
    [1] => Array
        (
            ['_id'] => "Group2"
            ['M'] => 0
            ['F'] => 0
        )
    [2] => Array
        (
            ['_id'] => "Group3"
            ['M'] => 0
            ['F'] => 0
        )
    [3] => Array
        (
            ['_id'] => "Group4"
            ['M'] => 0
            ['F'] => 0
        )
)


$array2 = Array
(
    [0] => Array
        (
            ['_id'] => "Group2"
            ['M'] => 180
            ['F'] => 200
        )
    [1] => Array
        (
            ['_id'] => "Group4"
            ['M'] => 360
            ['F'] => 500
        )
)

I want to compare the values of ['_id'] in both array and if they match, I will replace the values of ['M'] and ['F'] in array1 with those from array2 based on the corresponding ['_id].

So my desired ouptput would be:

$array1 = Array
(
    [0] => Array
        (
            ['_id'] => "Group1"
            ['M'] => 0
            ['F'] => 0
        )
    [1] => Array
        (
            ['_id'] => "Group2"
            ['M'] => 180
            ['F'] => 200
        )
    [2] => Array
        (
            ['_id'] => "Group3"
            ['M'] => 360
            ['F'] => 500
        )
    [3] => Array
        (
            ['_id'] => "Group4"
            ['M'] => 0
            ['F'] => 0
        )
)

This is my code but I can't seem to get the values replaced with the new values. The values are still the same as before.

foreach ($array1 as $defArr)
{
  foreach ($array2 as $dayArr)
  {
    if($dayArr['_id'] == $defArr['_id'])
    {
      $defArr['M'] = $dayArr['M'];
      $defArr['F'] = $dayArr['F'];
    }
  }
}
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2条回答

  • douli7841 douli7841 3年前

    This can be a one-character change:

    foreach ($array1 as $defArr)
    

    goes to

    foreach ($array1 as &$defArr)
    #                   ^
    

    The & reference operator points to the original sub array in the foreach loop context rather than a temporary variable.

    However, it's a bit safer to use the index explicitly:

    foreach ($array1 as $i => $defArr) {
        foreach ($array2 as $j => $dayArr) {
            if ($dayArr['_id'] == $defArr['_id']) {
                $array1[$i]['M'] = $array2[$j]['M'];
                $array1[$i]['F'] = $array2[$j]['F'];
            }
        }
    }
    

    If speed is important or $array2 is large, the time complexity of your algorithm is O(n * m). I recommend hashing $array2 for fast lookups as follows (O(n)):

    $lookup = array_reduce($array2, function ($a, $e) {
        $a[$e['_id']] = $e;
        return $a;
    });
    
    foreach ($array1 as $i => $e) {
        if (array_key_exists($e['_id'], $lookup)) {
            $array1[$i]['M'] = $lookup[$e['_id']]['M'];
            $array1[$i]['F'] = $lookup[$e['_id']]['F'];
        }
    }
    

    Try it!

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  • dongzhiyong8577 dongzhiyong8577 3年前
    <?php
    $array1 = [['_id'=>'abc','M'=>0,'F'=>0],['_id'=>'abcd','M'=>0,'F'=>0],['_id'=>'abcde','M'=>0,'F'=>0]];
    
    $array2 = [['_id'=>'abc','M'=>50,'F'=>300],['_id'=>'abcde','M'=>600,'F'=>700]];
    
    foreach($array2 as $key=> $array2value){
      $searched_in_array_1= array_search($array2value['_id'],array_column($array1,'_id'));
      if(is_numeric($searched_in_array_1)) $array1[$searched_in_array_1] = $array2value;
    }
    
    var_dump($array1);
    ?>
    

    You want to get a help with php array functions when dealing with arrays. I have used array_column and array_search functions for this

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