Backend DevelopmentPHP TutorialShare 4 ways to generate non-repeating random numbers and arrays in PHPShare 4 ways to generate non-repeating random numbers and arrays in PHP
Write below a few methods of generating non-repeating random numbers. Let’s go directly to the code.
The code is as follows:
<?phpdefine('RANDOM_MAX', 100);define('COUNT', 10);
echo 'max random num: '.RANDOM_MAX, ' ;result count:'.COUNT, '<br/>';
invoke_entry('rand1');invoke_entry('rand2');invoke_entry('rand3');invoke_entry('rand4');
function invoke_entry($func_name) { $time = new time(); $time->time_start(); call_user_func($func_name); echo $func_name.' time spend: ', $time->time_spend(); echo '<br/>';}function rand1() { $numbers = range (1, RANDOM_MAX); shuffle($numbers); //随机打乱数组 $result = array_slice($numbers, 1, COUNT); return $result;}function rand2() { $result = array(); while(count($result)< COUNT) { $result[] = mt_rand(1, RANDOM_MAX); //mt_rand()是比rand()更好更快的随机函数 $result = array_unique($result); //删除数组中重复的元素 } return $result;}function rand3() { $result = array(); while(count($result) < COUNT) { $_tmp = mt_rand(1, RANDOM_MAX); if(!in_array($_tmp, $result)) { //当数组中不存在相同的元素时，才允许插入 $result[] = $_tmp; } } return $result;}function rand4() { $result = array(); while (count($result) < COUNT) { $result[] = mt_rand(1, RANDOM_MAX); $result = array_flip(array_flip($result)); //array_flip将数组的key和value交换 } return $result;}class time { private $_start; public function time_start() { $this->_start = $this->microtime_float(); } public function time_spend() { return $this->microtime_float() - $this->_start; } private function microtime_float() { list($usec, $sec) = explode(" ", microtime()); return ((float)$usec + (float)$sec); }}
?> Let’s talk about the fourth method. , is the flip method. Use array_flip() to flip the keys and values of the array. Using the PHP array feature, the duplicate keys will be overwritten. At this time, flipping again is the same as removing the duplicate values. .
The above methods are just simple examples, and some methods have limited scope of application.
Let’s take a look at the efficiency of several methods:
Use array_unique() in Performance is poor when the array is large, and of course shuffle() will also be affected by this.
Related learning recommendations: PHP programming from entry to proficiency
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