<?php
$r = redEnvelope(100, 10, 12, 6);
echo array_sum($r); //校验结果
print_r($r); //查看分布
function redEnvelope($sum, $num, $max, $min){
$result = array_fill(0, $num, $min);
$loop = $sum - $num * $min;
$i = 0;
while($loop) {
$randNum = mt_rand(1, min($loop, $max - $min));
if($randNum && $result[$i] + $randNum <= $max) {
$result[$i] += $randNum;
$loop -= $randNum;
}
$i = ($i + 1) % $num;
} //分配结束
//$max 至多出现一次
$m = array_keys($result, max($result));
if(count($m) > 1 && $result[$m[0]] == $max) {
for($i=1; $i<count($m); $i++) {
$n = array_keys($result, min($result));
$result[$m[$i]]--;
$result[$n[0]]++;
}
}
//$min 至多出现一次
$m = array_keys($result, min($result));
if(count($m) > 1 && $result[$m[0]] == $min) {
for($i=1; $i<count($m); $i++) {
$n = array_keys($result, $min + 2);
$result[$m[$i]]++;
$result[$n[0]]--;
}
}
return $result;
}
红包算法
原文：http://www.cnblogs.com/csjoz/p/7244076.html
