PHP probability algorithm examples suitable for lottery programs and random advertisements_PHP tutorial

Then we will definitely design an algorithm in the program, that is, let the user win the prize according to a certain probability. Let’s first look at two probability algorithm functions.

Algorithm 1

Copy code The code is as follows:

/**
* Full probability calculation
*
* @param array $p array('a'=>0.5,'b'=>0.2,'c'=>0.4)
* @return string returns the key
of the above array* /
function random($ps){
static $arr = array();
$key = md5(serialize($ps));

if (!isset($arr[$key])) {
$max = array_sum($ps);
foreach ($ps as $k=>$v) {
$ v = $v / $max * 10000;
for ($i=0; $i<$v; $i++) $arr[$key][] = $k;
}
}
Return $arr[$key][mt_rand(0,count($arr[$key])-1)];
}

Algorithm 2

Copy code The code is as follows:

function get_rand($proArr) {
$result = '';

//Total probability accuracy of probability array
$proSum = array_sum($proArr);

//Probability array loop
foreach ($proArr as $key => $proCur) {
$randNum = mt_rand(1, $proSum);
if ($randNum <= $ proCur) {
                $result = $key;                                             🎜> unset ($proArr);

Return $result;
}

The above code is a classic probability algorithm. $proArr is a preset array. Assume that the array is: array(100,200,300,400), starting from 1 , within the probability range of 1000, screen whether the first number is within its occurrence probability range. If not, the probability is reduced, that is, the value of k minus the probability space of the number just now, in this case Subtract 100, which means that the second number is filtered within the range of 1,900. In this way, until the end, there will always be a number that meets the requirements. It's like touching something in a box. If the first one isn't there, the second one isn't there, and the third one isn't there, then the last one must be. This algorithm is simple and very efficient. The key is that this algorithm has been applied in our previous projects, especially in projects with large amounts of data. The efficiency is very good.
Next we configure the awards through PHP.

Copy code

The code is as follows:

$prize_arr = array( '0' => array('id '=>1,'prize'=>'tablet','v'=>1), '1' => array('id'=>2,'prize'=> ;'Digital camera','v'=>5), '2' => array('id'=>3,'prize'=>'Speaker device','v'=> ;10),

'3' => array('id'=>4,'prize'=>'4G USB flash drive','v'=>12),

'4' = > array('id'=>5,'prize'=>'10Q coins','v'=>22),
'5' => array('id'=>6 ,'prize'=>'You might win next time','v'=>50),
);

is a two-dimensional array that records all the draws Prize information, where id represents the winning level, prize represents the prize, and v represents the probability of winning. Note that v must be an integer. You can set the v of the corresponding award to 0, which means that the probability of winning the award is 0. The sum of v in the array (base). The larger the base, the more accurate the probability can be reflected. . In this example, the sum of v is 100, then the probability of winning for the tablet is 1%. If the sum of v is 10,000, the probability of winning is one in ten thousand.
Every time the front-end page is requested, PHP loops through the award setting array, and obtains the drawn award ID through the probability calculation function get_rand. Save the winning prizes in the array $res['yes'], and save the remaining non-winning information in $res['no'], and finally output the json number data to the front-end page.

Copy code

The code is as follows:

//If the winning data is placed in the database, you need to judge the number of winnings here
//If you win the 1st, 2nd, and 3rd prizes, if the maximum number is reached, unset the corresponding prizes to avoid duplication Winning the jackpot
//code here eg:unset($prize_arr['0'])
foreach ($prize_arr as $key => $val) {
$arr[$val['id' ]] = $val['v'];
}

$rid = get_rand($arr); //Get the award id based on probability

$res['yes'] = $prize_arr[$rid-1]['prize']; //Winning prizes
//Remove the winning prizes from the array, leaving the unwon prizes, if Database verification, you can omit here
unset($prize_arr[$rid-1]);
shuffle($prize_arr); //Disrupt the order of the array
for($i=0;$i< count($prize_arr);$i++){
$pr[] = $prize_arr[$i]['prize'];
}
$res['no'] = $pr;
echo json_encode($res);

Why can’t I draw the grand prize?

In many similar lottery activities, participants often cannot win the grand prize. The author will give you an example from a program perspective. If I am the organizer of the lottery event, I have set up 6 awards. Each award Different winning probabilities. If the first prize is a luxury car, but I set the winning probability to 0, what does this mean? This means that no matter how many draws, the lottery participants will never get this luxury car. And when the organizer flips the remaining squares every time, the participants will find that the first prize may be under a number next to the square that was just drawn, and they blame their bad luck. Is it really bad luck? In fact, when the participant flipped that square, the program had already determined the prize, but when he flipped the other squares to see the prize, he saw just a *, which confused the audience and participants. I think after reading this article, you may know that the flip lottery in TV shows is tricky, and you may never choose a double color ball by machine again.

http://www.bkjia.com/PHPjc/751513.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/751513.htmlTechArticle Then we will definitely design an algorithm in the program, that is, let the user win the prize according to a certain probability. Let’s first look at two probability algorithm functions. Algorithm 1 Copy code The code is as follows: /** * All...