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php method to implement array deduplication: 1. Use the array_unique method to deduplicate array elements; 2. Use the array_flip method to deduplicate.
The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer
php array element quick deduplication
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. Efficiency of using array_unique method to remove duplicates
<?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 'unique count:'.count($arr).'<br>'; echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms<br>'; echo 'use memory:'.getUseMemory(); /** * 获取使用内存 * @return float */ function getUseMemory(){ $use_memory = round(memory_get_usage(true)/1024,2).'kb'; return $use_memory; } /** * 获取microtime * @return float */ function getMicrotime(){ list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec; } ?>
unique count:99 run time:653.39303016663ms use memory:5120kb
Using array_unique method to remove duplicates takes about 650ms to run and takes up about 5m of memory
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 be to 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 'unique count:'.count($arr).'<br>'; echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms<br>'; echo 'use memory:'.getUseMemory(); /** * 获取使用内存 * @return float */ function getUseMemory(){ $use_memory = round(memory_get_usage(true)/1024,2).'kb'; return $use_memory; } /** * 获取microtime * @return float */ function getMicrotime(){ list($usec, $sec) = explode(' ', microtime()); return (float)$usec + (float)$sec; } ?>
unique count:99 run time:12.840032577515ms use memory:768kb
Using the array_flip method to deduplicate, the running time takes about 18ms, and the memory usage is about 2m
Therefore, using the array_flip method to deduplicate the running time is 98% shorter than using the array_unique method, and the memory usage is reduced by 4/ 5;
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