PHP 生成随机红包算法

<?php
/*
 * Note: 红包生成随机算法
 */
class Reward
{
 public $rewardMoney; // 红包金额、单位元
 public $rewardNum; // 红包数量
 // 执行红包生成算法
 public function splitReward($rewardMoney, $rewardNum, $max, $min)
 {
 // 传入红包金额和数量，因为小数在计算过程中会出现很大误差，所以我们直接把金额放大100倍，后面的计算全部用整数进行
 $min = $min * 100;
 $max = $max * 100;
 // 预留出一部分钱作为误差补偿，保证每个红包至少有一个最小值
 $this->rewardMoney = $rewardMoney * 100 - $rewardNum * $min;
 $this->rewardNum = $rewardNum;
 // 计算出发出红包的平均概率值、精确到小数4位。
 $avgRand = 1 / $this->rewardNum;
 $randArr = [];
 // 定义生成的数据总合sum
 $sum = 0;
 $t_count = 0;
 while ($t_count < $rewardNum) {
 // 随机产出四个区间的额度
 $c = rand(1, 100);
 if ($c < 15) {
 $t = round(sqrt(mt_rand(1, 1500)));
 } else if ($c < 65) {
 $t = round(sqrt(mt_rand(1500, 6500)));
 } else if ($c < 95) {
 $t = round(sqrt(mt_rand(6500, 9500)));
 } else {
 $t = round(sqrt(mt_rand(9500, 10000)));
 }
 ++$t_count;
 $sum += $t;
 $randArr[] = $t;
 }
 // 计算当前生成的随机数的平均值，保留4位小数
 $randAll = round($sum / $rewardNum, 4);
 // 为将生成的随机数的平均值变成我们要的1/N，计算一下每个随机数要除以的总基数mixrand。此处可以约等处理，产生的误差后边会找齐
 // 总基数 = 均值/平均概率
 $mixrand = round($randAll / $avgRand, 4);
 // 对每一个随机数进行处理，并乘以总金额数来得出这个红包的金额。
 $rewardArr = array();
 foreach ($randArr as $key => $randVal) {
 // 单个红包所占比例randVal
 $randVal = round($randVal / $mixrand, 4);
 // 算出单个红包金额
 $single = floor($this->rewardMoney * $randVal);
 // 小于最小值直接给最小值
 if ($single < $min) {
 $single += $min;
 }
 // 大于最大值直接给最大值
 if ($single > $max) {
 $single = $max;
 }
 // 将红包放入结果数组
 $rewardArr[] = $single;
 }
 // 对比红包总数的差异、将差值放在第一个红包上
 $rewardAll = array_sum($rewardArr);
 // 此处应使用真正的总金额rewardMoney，$rewardArr[0]可能小于0
 $rewardArr[0] = $rewardMoney * 100 - ($rewardAll - $rewardArr[0]);
 // 第一个红包小于0时,做修正
 if ($rewardArr[0] < 0) {
 rsort($rewardArr);
 $this->add($rewardArr, $min);
 }
 rsort($rewardArr);
 // 随机生成的最大值大于指定最大值
 if ($rewardArr[0] > $max) {
 // 差额
 $diff = 0;
 foreach ($rewardArr as $k => &$v) {
 if ($v > $max) {
 $diff += $v - $max;
 $v = $max;
 } else {
 break;
 }
 }
 $transfer = round($diff / ($this->rewardNum - $k + 1));
 $this->diff($diff, $rewardArr, $max, $min, $transfer, $k);
 }
 return $rewardArr;
 }
 // 处理所有超过最大值的红包
 public function diff($diff, &$rewardArr, $max, $min, $transfer, $k)
 {
 // 将多余的钱均摊给小于最大值的红包
 for ($i = $k; $i < $this->rewardNum; $i++) {
 // 造随机值
 if ($transfer > $min * 20) {
 $aa = rand($min, $min * 20);
 if ($i % 2) {
 $transfer += $aa;
 } else {
 $transfer -= $aa;
 }
 }
 if ($rewardArr[$i] + $transfer > $max) continue;
 if ($diff - $transfer < 0) {
 $rewardArr[$i] += $diff;
 $diff = 0;
 break;
 }
 $rewardArr[$i] += $transfer;
 $diff -= $transfer;
 }
 if ($diff > 0) {
 $i++;
 $this->diff($diff, $rewardArr, $max, $min, $transfer, $k);
 }
 }
 // 第一个红包小于0,从大红包上往下减
 public function add(&$rewardArr, $min)
 {
 foreach ($rewardArr as &$re) {
 $dev = floor($re / $min);
 if ($dev > 2) {
 $transfer = $min * floor($dev / 2);
 $re -= $transfer;
 $rewardArr[$this->rewardNum - 1] += $transfer;
 } elseif ($dev == 2) {
 $re -= $min;
 $rewardArr[$this->rewardNum - 1] += $min;
 } else {
 break;
 }
 }
 if ($rewardArr[$this->rewardNum - 1] > $min || $rewardArr[$this->rewardNum - 1] == $min) {
 return;
 } else {
 $this->add($rewardArr, $min);
 }
 }
}

<?php
class CreateReward{
 /*
 * 生成红包
 * @param int $total 红包总金额
 * @param int $num 红包总数量
 * @param int $max 红包最大值
 *
 */
 public function random_red($total, $num, $max, $min)
 {
 // 总共要发的红包金额，留出一个最大值;
 $total = $total - $max;
 $reward = new Reward();
 $result_merge = $reward->splitReward($total, $num, $max - 0.01, $min);
 sort($result_merge);
 $result_merge[1] = $result_merge[1] + $result_merge[0];
 $result_merge[0] = $max * 100;
 foreach ($result_merge as &$v) {
 $v = floor($v) / 100;
 }
 return $result_merge;
 }
}

<?php
/**
 * Created by PhpStorm.
 * User: lufei
 * Date: 2017/1/4
 * Time: 22:49
 */
header('content-type:text/html;charset=utf-8');
ini_set('memory_limit', '128M');
require_once('CreateReward.php');
require_once('Reward.php');
$total = 50000;
$num = 300000;
$max = 50;
$min = 0.01;
$create_reward = new CreateReward();

for ($i=0; $i<5; $i++) {
 $time_start = microtime_float();
 $reward_arr = $create_reward->random_red($total, $num, $max, $min);
 $time_end = microtime_float();
 $time[] = $time_end - $time_start;
}
echo array_sum($time)/5;
function microtime_float()
{
 list($usec, $sec) = explode(" ", microtime());
 return ((float)$usec + (float)$sec);
}

$reward_arr = $create_reward->random_red($total, $num, $max, $min);
sort($reward_arr);//正序，最小的在前面
$sum = 0;
$min_count = 0;
$max_count = 0;
foreach($reward_arr as $i => $val) {
 if ($i<3) {
 echo "<br />第".($i+1)."个红包，金额为：".$val."<br />";
 }
 if ($val == $max) {
 $max_count++;
 }
 if ($val < $min) {
 $min_count++;
 }
 $val = $val*100;
 $sum += $val;
}
//检测钱是否全部发完
echo '<hr>已生成红包总金额为：'.($sum/100).';总个数为：'.count($reward_arr).'<hr>';
//检测有没有小于0的值
echo "<br />最大值:".($val/100).',共有'.$max_count.'个最大值，共有'.$min_count.'个值比最小值小';

$reward_arr = $create_reward->random_red($total, $num, $max, $min);
$show = array();
rsort($reward_arr);
// 为了更直观的显示正态分布效果,需要将数组重新排序
foreach($reward_arr as $k=>$value)
{
 $t=$k%2;
 if(!$t) $show[]=$value;;
 else array_unshift($show,$value);
}
echo "设定最大值为:".$max.',最小值为:'.$min.'<hr />';
echo "<table style='font-size:12px;width:600px;border:1px solid #ccc;text-align:left;'><tr><td>红包金额</td><td>图示</td></tr>";
foreach($show as $val)
{
 // 线条长度计算
 $width=intval($num*$val*300/$total);
 echo "<tr><td> {$val} </td><td width='500px;text-align:left;'><hr style='width:{$width}px;height:3px;border:none;border-top:3px double red;margin:0 auto 0 0px;'></td></tr>";
}
echo "</table>";