红包算法

min 最小金额
max 最大金额
total 剩余总金额
num 剩余总人数

if (num == 1)
{
   return total
}

// 更新随机种子  

srand(time(NULL));

// 确定本次随机范围

LONG low = (total – (num-1) * max) < min ? min : total – (num-1) * max;

LONG high = (total – (num-1) * max) > max ? max : (total – (num-1)*min);

LONG ave = total / num > 1 ? total / num : 1;

// 调整上限
if (high > 2 * ave) high = 2 * ave;

// 生成随机支
LONG ram = random() % high;

// 防止溢出
if (ram < low) ram = low;

if (ram > high) ram = high;

return ram;

@算法二

 100元发10个红包，100元换算为分是10000，则这个随机数范围是1-9999，生成9个不重复的随机数并排序，假设为n1-n9，n0=0，n10=10000，则10个红包的钱分别是n1-n0…n10-n9，再换算为元

代码
$ cat split.php

    <?php
    $packs = split_money(100, 10);
    var_dump($packs);

    function split_money($money, $count) {
      $money *= 100;
      $list = array(0);
      for ($i = 1; $i < $count; ++$i) {
        while(in_array($r = mt_rand(1, $money), $list));
        $list[] = $r;
      }
      sort($list);
      $list[] = $money;
      $packs = array();
      for ($i = 0; $i < $count; ++$i)
        $packs[] = ($list[$i + 1] – $list[$i]) / 100;
      return $packs;
    }


    array(10) {
      [0] =>
      double(23.09)
      [1] =>
      double(33.62)
      [2] =>
      double(0.71)
      [3] =>
      double(19.3)
      [4] =>
      double(0.24)
      [5] =>
      double(0.47)
      [6] =>
      double(5.52)
      [7] =>
      double(2.32)
      [8] =>
      double(5.47)
      [9] =>
      double(9.26)
    }