How to implement the PHP array element fast Redo effect

1. Use the Array_unique method to remove the weight

To de-weigh the elements of an array, we generally use the Array_unique method, which can be used to weigh the elements in the arrays.

<?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);p Rint_r ( $arr);? >

Output:

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

After the weight is gone, the key values are not in order, and the key values can be reordered by using Array_values.

2. Using the Array_unique method to remove weight efficiency

<?php$arr = Array ();//Create an array of 100,000 random elements for ($i =0; $i <100000; $i + +) {    $arr [] = Mt_rand (1,99);} Record start Time $starttime = Getmicrotime ();//$arr = Array_unique ($arr);//record end time $endtime = Getmicrotime (); $arr = Array_value S ($arr); Echo ' unique count: '. Count ($arr). ' <br> '; Echo ' run Time: '. (float) (($endtime-$starttime) *1000). ' Ms<br> '; Echo ' use Memory: '. Getusememory ();/** * Get memory using * @return float */function getusememory () {    $use _memory = Round (Memory_get_usage (True)/1024,2). ' KB ';    return $use _memory;} /** * Get microtime * @return float */function getmicrotime () {    list ($usec, $sec) = Explode (', microtime ());    return (float) $usec + (float) $sec;}? >

Unique count:99
Run TIME:653.39303016663MS
Use MEMORY:5120KB

Use Array_unique method to go heavy, run time takes about 650ms, memory occupies about 5m

3. Faster array de-weight method

PHP has a key-value interchange method Array_flip, we can use this method to go heavy, because the key value interchange, the original duplicate value will become the same key.
Then do a key exchange, the key and the value back can be done to the weight.

<?php$arr = Array ();//Create an array of 100,000 random elements for ($i =0; $i <100000; $i + +) {    $arr [] = Mt_rand (1,99);} Record start Time $starttime = Getmicrotime ();//Use key value interchange to $arr = Array_flip ($arr); $arr = Array_flip ($arr);//record end time $endtime = Getmi Crotime (); $arr = Array_values ($arr); Echo ' unique count: '. Count ($arr). ' <br> '; Echo ' run Time: '. (float) (($endtime-$starttime) *1000). ' Ms<br> '; Echo ' use Memory: '. Getusememory ();/** * Get memory using * @return float */function getusememory () {    $use _memory = Round (Memory_get_usage (True)/1024,2). ' KB ';    return $use _memory;} /** * Get microtime * @return float */function getmicrotime () {    list ($usec, $sec) = Explode (', microtime ());    return (float) $usec + (float) $sec;}? >

Unique count:99
Run time:12.840032577515ms
Use memory:768kb

Use Array_flip method to go heavy, run time takes about 18ms, memory occupies about 2m

Therefore, using the array_flip method to reduce the time-to-weight ratio using array_unique method reduces the 98%and memory consumption 4/5;

This article explains how to implement the PHP array elements to quickly redo the effect, more relevant content please focus on PHP Chinese web.

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