Question

我有一个非常大的数据集，我正在尝试找到满足所有数据集的最小集合。最终集必须在其中包含一个在所有数据集中的值

一小部分数据样本

[0] => Array
    (
        [0] => 21
        [1] => 21
        [2] => 21
    )

[1] => Array
    (
        [0] => 29
    )

[2] => Array
    (
        [0] => 27
    )

[3] => Array
    (
        [0] => 21
        [1] => 21
        [2] => 21
        [3] => 39
        [4] => 39
        [5] => 43
    )

[4] => Array
    (
        [0] => 29
        [1] => 33
        [2] => 33
        [3] => 43
    )

在这种情况下，我需要逻辑来返回21,27和29 返回的值必须是与所有数组匹配的最小值。由于我是PHP程序员，我在PHP中编写此函数。

Answer 1

您可以遵循此算法：

测试后更新

$data=array(
            array(21,29,27,57,22),
            array(22,21,23,24,25,26),
            array(31)
            );

$map = array(); // keep a map of values and how many times they occur in other sets
foreach ($data as $setid => $set) {
    foreach (array_unique($set) as $v) {
        $map[$v][$setid] = true;
    }
}

function reverseCount(array $a, array $b)
{
    return count($b) - count($a);
}

// sort reversed on intersection count
uasort($map, 'reverseCount');

// after sorting the first number will be the one that occurs the most
// keep track of which sets have been hit
$setmap = array(); $n = count($data);
foreach ($map as $v => $sets) {
    $hits = 0;
    foreach ($sets as $setid => $dummy) {
        if (!isset($setmap[$setid])) {
            --$n;
            ++$hits;
            $setmap[$setid] = true;
        } else {
            continue;
        }
    }
    if ($hits) {
        echo "value $v\n";
        if (!$n) {
            // all sets are hit
            break;
        }
    }
}

这次测试了。事实并没有证明总能得到正确的结果，因为这被认为是一种贪婪的近似算法。

但我希望它能说明你能做些什么。如果有什么事情让您感到困惑，或者我对它有任何不妥之处，请告诉我。）

最小匹配逻辑

1 个答案: