How to implement array deduplication in php

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.

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

'; echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms
'; 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.

'; echo 'run time:'.(float)(($endtime-$starttime)*1000).'ms
'; 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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