How to implement repeated number statistics in arrays in PHP (code)

The content of this article is about how to implement array repeated number statistics (code) in PHP. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

All numbers in an array of length n are in the range of 0 to n-1. Some numbers in the array are repeated, but I don't know how many numbers are repeated. I don't know how many times each number is repeated. Please find any repeated number in the array. For example, if the input is an array {2,3,1,0,2,5,3} of length 7, then the corresponding output is the first repeated number 2.
1. Hash method
2. Define a backup array, used as a hash, the key is each element of the original array, the value is the number of occurrences
3. Traverse the hash array

hash for i=0i;
      
$v){ if($v>=2){ $flag=true; $duplication[0]=$k; break; } } return $flag; } $arr=[2,1,3,0,4]; $res=duplicate($arr,$duplication); var_dump($res); var_dump($duplication);
      
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