How to achieve quick deduplication effect of php array elements

1. Use the array_unique method to deduplicate

To deduplicate array elements, we generally use the array_unique method. This method can deduplicate the elements in the array.

<?php$arr = array(1,1,2,3,3,3,4,4,5,6,6,7,8,8,9,9,9);$arr = array_unique($arr);$arr = array_values($arr);
print_r($arr);?>

Output:

Array(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => 5
    [5] => 6
    [6] => 7
    [7] => 8
    [8] => 9)

After deduplication, the key values ​​will be out of order. You can use array_values ​​to reorder the key values.

2. Use array_unique method to remove duplicates for efficiency

<?php$arr = array();// 创建100000个随机元素的数组for($i=0; $i<100000; $i++){    $arr[] = mt_rand(1,99);
}// 记录开始时间$starttime = getMicrotime();// 去重$arr = array_unique($arr);// 记录结束时间$endtime = getMicrotime();$arr = array_values($arr);echo &#39;unique count:&#39;.count($arr).&#39;<br>&#39;;echo &#39;run time:&#39;.(float)(($endtime-$starttime)*1000).&#39;ms<br>&#39;;echo &#39;use memory:&#39;.getUseMemory();/**
 * 获取使用内存
 * @return float
 */function getUseMemory(){
    $use_memory = round(memory_get_usage(true)/1024,2).&#39;kb&#39;;    return $use_memory;
}/**
 * 获取microtime
 * @return float
 */function getMicrotime(){
    list($usec, $sec) = explode(&#39; &#39;, microtime());    return (float)$usec + (float)$sec;
}?>

unique count:99
run time:653.39303016663ms
use memory:5120kb

Use the array_unique method to remove duplicates. The running time takes about 650ms and the memory usage is about 5m

3. Faster Array deduplication method

php has a key-value exchange method array_flip. We can use this method to deduplicate. Because of key-value exchange, the original duplicate values ​​will become the same key.
Then perform a key-value exchange and exchange the keys and values ​​back to complete deduplication.

<?php$arr = array();// 创建100000个随机元素的数组for($i=0; $i<100000; $i++){    $arr[] = mt_rand(1,99);
}// 记录开始时间$starttime = getMicrotime();// 使用键值互换去重$arr = array_flip($arr);$arr = array_flip($arr);// 记录结束时间$endtime = getMicrotime();$arr = array_values($arr);echo &#39;unique count:&#39;.count($arr).&#39;<br>&#39;;echo &#39;run time:&#39;.(float)(($endtime-$starttime)*1000).&#39;ms<br>&#39;;echo &#39;use memory:&#39;.getUseMemory();/**
 * 获取使用内存
 * @return float
 */function getUseMemory(){
    $use_memory = round(memory_get_usage(true)/1024,2).&#39;kb&#39;;    return $use_memory;
}/**
 * 获取microtime
 * @return float
 */function getMicrotime(){
    list($usec, $sec) = explode(&#39; &#39;, microtime());    return (float)$usec + (float)$sec;
}?>

unique count:99
run time:12.840032577515ms
use memory:768kb

Use array_flip method to remove duplicates, the running time takes about 18ms, the memory usage is about 2m

. Therefore, using the array_flip method to remove duplicates takes longer than using the array_unique method. The running time is 98%, memory usage reduced4/5;

This article explains how to achieve the rapid deduplication effect of PHP array elements. For more related content, please pay attention to the PHP Chinese website.

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