How to quickly remove duplicate elements from php arrays-PHP Tutorial-php.cn

How to quickly remove duplicate elements from php arrays

墨辰丷

Release： 2023-03-27 14:30:02

Original

2067 people have browsed it

This article mainly introduces the method of quickly deduplicating PHP array elements, which has a good reference value. Let’s take a look at it with the editor

1. Use the array_unique method to deduplicate

To deduplicate array elements, we generally use the array_unique method, using This method can remove duplicate elements from 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);
?>

Copy after login

Output:

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

Copy after login

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;
}
?>

Copy after login

unique count:99
run time:653.39303016663 ms
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 key-value exchange, The original duplicate value will become the same key.

Then perform a key-value exchange again, 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;
}
?>

Copy after login

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

USEarray_flipMethod to remove duplicates, the running time takes about 18ms, and the memory usage is about 2m

, so using the array_flip method to remove duplicates is better than using array_uniqueThe method running time is reduced by 98%, and the memory usage is reduced by 4/5;

Related recommendations:

How to use array_sum() to calculate the sum of array elementsvalue

php double quotes when accessing array elementserror reporting How to handle

jquery operation objectArray elementMethod summary (with case)

The above is the detailed content of How to quickly remove duplicate elements from php arrays. For more information, please follow other related articles on the PHP Chinese website!