Analysis of the method of generating non-repeating random numbers in php

function get_randoms($min,$max,$num){
 $count = 0;
 $res = array();
 while($count<$num){
 $res [] = mt_random($min,$max);
 $res = array_flip(array_flip($res));
 $count = count($res);
 }
 return $res;
 }

$result = get_randoms (1,60,10);
?>

Here he uses $count to get the number of result arrays, and he makes the number of result arrays less than the target number in the while loop. Through this, we get $count which is an array of target number. (bbs.it-home.org Scripting School) During this period, in each cycle, through mt_random($min,$max), a value within the range is randomly obtained and stored in the array $res, and then through two key-value exchanges, that is, through the uniqueness of the array key, Make sure there is no repetition.

After I read the code of this logic, I couldn't help but think deeply. What would you do if you didn't know the array_filp function? To put it bluntly, it uses the uniqueness of the key so that there will be no duplication of random numbers. So can we simplify this problem?

Code:

function get_randoms($min,$max,$num){
 $count = 0;
 $res = array();
 while($count<$num){
 $ key = mt_random($min,$max);
 $res[$key] = $key;
 $count = count($res);
 }
 return $res;
}
$result = get_randoms(1,60 ,10);
?>

This solves this problem completely through the uniqueness of the array key. array_flip will not be used at all.

Summary: 1. Because PHP provides a large number of built-in functions, their execution efficiency is very high. (bbs.it-home.org Programmer’s Home) When you encounter a problem, try to use it to solve the problem as much as possible. This is convenient and fast.

2. PHP provides a large number of built-in functions, and the execution efficiency is also very high. However, although the efficiency is high, it still takes time to execute. When you encounter a problem, don't do it blindly. You can first see the essence of the solution so that you can implement it skillfully.