How to quickly remove duplicate elements from php arrays

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);
?>

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:653.39303016663 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;
}
?>

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;

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