How to improve the process of generating non-repeated random numbers?

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How to improve the process of generating non-repeated random numbers?

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#1 by (6 votes)
#2 by (4 votes)

4

I have a algorithm for creating random numbers for lottery that have the following characteristics:

1 ° You must be informed of the number of numbers to be generated.

2 ° Numbers can not be repeated.

3 ° The numbers need to be in ascending order.

As a beginner in PHP, I tried to make the algorithm work. To do this, I created a class with a geraNumeros() function recursively in order to do all these items and return an array where I sort using asort() and then transform into string with implode() . Is there any way to optimize it?

<?php

class loterias{

   public function geraNumero($aQuantidade, $aMinimo, $aMaximo) {

      $contador = 0;
      $result = array();
      while ($aQuantidade):
         $result[$aQuantidade] = str_pad(rand($aMinimo, $aMaximo), 2, '0', STR_PAD_LEFT);
         $aQuantidade--;
         $contador++;
      endwhile;
      while ($contador !== count(array_unique($result))):
         $result = $this->geraNumero($contador, $aMinimo, $aMaximo);
      endwhile;
      return $result;
   }

}

// Parametros //
$quantidade = 6;
$minimo = 1;
$maximo = 60;

$mega = new loterias();
$result = $mega->geraNumero($quantidade, $minimo, $maximo);
asort($result);
var_dump($result);

php

asked by anonymous 08.01.2015 / 19:25

2 answers

4

I leave a solution that, in my opinion, has a simple code:

<?php

class loterias{

   public function geraNumero($aQuantidade, $aMinimo, $aMaximo) {
       if( $aQuantidade > ($aMaximo - $aMinimo) ) {
           return false;
       }

       $numeros = range($aMinimo, $aMaximo);
       shuffle($numeros);
       array_splice($numeros, 0, $aQuantidade);
       sort($numeros);
       return $numeros;
   }

}

Requirements can not be satisfied if the difference between the maximum and minimum are less than the quantity, so I did this validation (could have thrown an exception).

An array is created with all possible numbers.
Then they are shuffled with the "shuffle" function.
The first ones are chosen in the specified amount.
Are ordered.

10.01.2015 / 20:45

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score 6 · Accepted Answer

With some functions for arrays I got the same result, here's an explanation of what each function does:

range() - Creates an array from a minimum to a maximum.

array_rand() - Randomly returns a key from an array. With the second parameter you can specify the number of elements you want to return.

array_flip() - Invert the value with the key of an array. I did this because in PHP the keys start with zero, and I think lotteries do not start with zero.

array_map() - For each element of an array, it performs a certain function, in the if it would be str_pad with the required parameters.

<?php

function geraNumeros($quantidade, $minimo, $maximo)
{
    $listaDeNumeros = range($minimo, $maximo);
    $numeros = array_rand(array_flip($listaDeNumeros), $quantidade);

    $numeros = array_map(function($value){
        return str_pad($value, 2, '0', STR_PAD_LEFT);   
    }, $numeros);

    return implode($numeros, ',');
}

echo geraNumeros(6, 1, 60) . PHP_EOL;
echo geraNumeros(6, 1, 60) . PHP_EOL;
echo geraNumeros(6, 1, 60) . PHP_EOL;
echo geraNumeros(6, 1, 60) . PHP_EOL;

Example on Ideone.