在PHP中找到最大频率元素的最快方法

Question

I have an array of ids like 127415157,31323794... (range not known). What is the quickest way to find the max frequency ID in PHP?

$array_ids = array()

Answer 1

// Gives us an associative array of id=>count mappings,
$counts = array_count_values($array_ids);
// and sorts it from largest to smallest count
arsort($counts);

// Gets the first key after sorting, which is the id with the largest count
$max_freq_id = key($counts);

The suggestion of using array_search() combined with max() may be faster than this, however, since it doesn't need to completely sort the array, and thus will run in O(n) time instead of O(n log n) .

Answer 2

$a = array(1, 2, 3, 4, 3, 3, 4, 4, 1, 3);
$r = array_count_values($a);
$k = array_search(max($r), $r);
echo "most frequent value is $k";

Answer 3

Addressing the issue of multiple elements with same frequency:

$values = array(1, 1, 3, 3, 3, 3, 4, 5, 5, 5, 5, 6); 
$freq   = array_count_values($values);
arsort($freq);
$max = $val = key($freq); 
while(next($freq) && current($freq) == $freq[$max]){
    $val .= ','.key($freq);
}

echo " most frequent value is/are $val ";

this will ouput

most frequent value is/are 5,3

also, it's a little faster than using array_search and max combo...

Answer 4

尝试最大

$max = max($array_ids);