152 lines
3.6 KiB
PHP
152 lines
3.6 KiB
PHP
<?php
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namespace Kiri\Rpc;
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use Exception;
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class Luckdraw
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{
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/**
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* @param array $goods
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* @param string $wight
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* @return mixed
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* @array = [
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ['name'=> '商品名称', 'probability'=> '概率', 'total'=> '库存'],
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* ]
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*
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* @uses $reward = Lucked::luck($data);
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*/
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public static function luck(array $goods, string $wight = 'probability'): mixed
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{
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static $class = null;
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if ($class === null) $class = new Luckdraw();
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if (empty($goods)) return null;
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$array = $prob = $alias = [];
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$defaultIndex = 0;
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foreach ($goods as $key => $val) {
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if ($val[$wight] == 0) $defaultIndex = $key;
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$array[] = (float)$val[$wight];
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}
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$array[$defaultIndex] = 1 - array_sum($array);
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$class->ket($array, $prob, $alias);
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$result = $class->generation($array, $prob, $alias);
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if (!isset($goods[$result])) {
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return null;
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}
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return $goods[$result];
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}
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/**
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* @param $data
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* @param $prob
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* @param $alias
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* @return mixed
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*/
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private function generation($data, $prob, $alias): mixed
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{
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$nums = count($prob) - 1;
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$MAX_P = $this->getMin($data); // 假设最小的几率是万分之一
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$coin_toss = rand(1, $MAX_P) / $MAX_P; // 抛出硬币
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$col = rand(0, $nums); // 随机落在一列
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$b_head = $coin_toss < $prob[$col]; // 判断是否落在原色
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return $b_head ? $col : @$alias[$col];
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}
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/**
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* @param $num
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* @return string
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*/
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private function getMin($num): string
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{
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$def = current($num);
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foreach ($num as $val) {
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if ($val < $def) {
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$def = $val;
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}
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}
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$length = $this->getFloatLength($def) + 1;
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return sprintf('1%0' . $length . 'd', 0);
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}
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/**
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* @param $float
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* @return int
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*/
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private function getFloatLength($float): int
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{
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$ex = explode('.', 1 - $float);
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return strlen(end($ex));
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}
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/**
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* @param array $data
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* @param array $prob
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* @param array $alias
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*/
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private function ket(array $data, array &$prob, array &$alias)
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{
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$nums = count($data);
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$small = $large = [];
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for ($i = 0; $i < $nums; ++$i) {
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$data[$i] = $data[$i] * $nums; // 扩大倍数，使每列高度可为1
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/** 分到两个数组，便于组合 */
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if ($data[$i] < 1) {
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$small[] = $i;
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} else {
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$large[] = $i;
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}
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}
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/** 将超过1的色块与原色拼凑成1 */
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while (!empty($small) && !empty($large)) {
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$n_index = array_shift($small);
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$a_index = array_shift($large);
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$prob[$n_index] = $data[$n_index];
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$alias[$n_index] = $a_index;
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// 重新调整大色块
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$data[$a_index] = ($data[$a_index] + $data[$n_index]) - 1;
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if ($data[$a_index] < 1) {
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$small[] = $a_index;
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} else {
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$large[] = $a_index;
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}
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}
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/** 剩下大色块都设为1 */
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while (!empty($large)) {
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$n_index = array_shift($large);
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$prob[$n_index] = 1;
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}
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/** 一般是精度问题才会执行这一步 */
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while (!empty($small)) {
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$n_index = array_shift($small);
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$prob[$n_index] = 1;
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}
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}
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}
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