PHP切割整数工具类似微信红包金额分配的思路详解

 Composer地址：https://packagist.org/packages/werbenhu/php-number-slicing

GitHub地址：https://github.com/werbenhu/php-number-slicing

主要代码：NumberSlicing.php

思路：将数字按精度放大倍数，比如切割数字1，切割的份数是10，精度是0.01，则将1放大100 X 10倍，然后再来对加了1000倍权重后的值进行切割。切割完成之后，再将权重去除，保证总值是1。

<?php
namespace Werben\Tools;
use Exception;
class NumberSlicing {
 /**
  * 精确小数点，舍弃最后一位之后的数据（非四舍五入）
  * floor with precision
  * @param $number 要精确的数
  * @param $precision 精度，比如保留到0.01，则该值为2
  * @return float|int
  */
 public static function floorWithPrecision($number, $precision) {
  $power = pow(10, $precision);
  $ret = floor($number * $power) * 1.0 / $power ;
  return $ret;
 }
 /**
  * 精确小数点，按四舍五入保留最后一位
  * round with precision
  * @param $number 要精确的数
  * @param $precision 精度，比如保留到0.01，则该值为2
  * @return float|int
  */
 public static function roundWithPrecision($number, $precision) {
  $power = pow(10, $precision);
  $ret = round($number * $power) * 1.0 / $power ;
  return $ret;
 }
 /**
  * 将数把权重放大，比如1，要按精度0.0001分配，则先将1乘以10000然后再来分配
  * random the sum weights 加上权重之后，整个要切割的数的权重总值
  * @param $weight_items 用来保留，随机分配的权重值
  * @param $count 要切割的份数
  * @param int $each_weight 加上权重之后，每一份平均的权重值
  * @param int $min_weight 加上权重之后，最小额度的值
  * @return float|int
  */
 public static function weightSlicing(&$weight_items, $count, $each_weight = 10, $min_weight = 3)
 {
  $already_count = count($weight_items);
  $cur_random_full_total = ($already_count + 1) * $each_weight;
  $already_random_real_total = 0;
  foreach ($weight_items as $value) {
   $already_random_real_total += $value;
  }
  $cur_random_rest = $cur_random_full_total - $already_random_real_total;
  if ($already_count == $count - 1) {
   $cur_random_rate = $cur_random_rest;
  } else {
   $cur_random_rate_max = $cur_random_rest + $each_weight - $min_weight * 2;
   $cur_random_rate = $min_weight + mt_rand(0, $cur_random_rate_max);
  }
  $weight_items[] = $cur_random_rate;
  return $cur_random_rate;
 }
 /**
  * slicing the number
  * @param int $number
  * @param int $size
  * @param float $precision
  * @param float $min
  * @return array
  * @throws Exception
  */
 public static function numberSlicing($number, $size, $precision = 0.01, $min = 0.01) {
  if ($number * 1.0 / $size <= $min) {
   throw new Exception('min number is bigger than the average value!');
  }
  if ($precision > 1) {
   throw new Exception('precision can\'t bigger than 1!');
  }
  if ($min < $precision) {
   throw new Exception('precision can\'t bigger than min!');
  }
  $weight_items = [];
  $items = [];
  //不加权重情况下，每一份的平均值
  $each_weight = intval($number / $size);
  if ($precision < 1) {
   //如果精度是小数
   if ($each_weight > 1) {
    //如果平均值大于1，则最小额度则直接用min就可以了
    //每一份的平均值乘以权重的值，比如精度为0.01，则每一份的平均值要乘以权重（100）
    $each_weight = intval((1 / $precision) * $number / $size);
    //最小数值也要乘以权重
    $min_weight = intval(1 / $precision) * $min;
   } else {
    //如果平均值小于1，需要将平均值也乘以权重
    $each_weight = intval(1 / $precision);
    $min_weight = $each_weight * $size * $min / $number;
   }
   $precision_num = log10(1 / $precision);
  } else {
   //如果精度是整数(1)
   $min_weight = $min;
   $precision_num = 0;
  }
  $sum_item_number = 0.0;
  $sum_weight = 0.0;
  //先将整个数，随机按最小额度分配
  for ($i = 0; $i < $size; $i++) {
   $cur_weight = self::weightSlicing($weight_items, $size, $each_weight, $min_weight);
   //将权重去除，换算回原先的比例
   $rate = ($number * $cur_weight * 1.00) / ($size * $each_weight);
   $rate = self::floorWithPrecision($rate, $precision_num);
   $sum_item_number += $rate;
   $sum_weight += $cur_weight;
   $items[] = $rate;
  }
  //由于误差，随机分配后，还会遗留一些数没有完全分配完，则将剩下的数随机分配
  if ($precision_num != 0) {
   //如果是切割成小数
   $rest = $number - $sum_item_number;
   while ($rest - 0.00 > PHP_FLOAT_MIN) {
    if ($rest / $min >= 1.0) {
     //剩余的数大于min最小额度，则将每份最小额度随机分配
     $random_index = mt_rand(0, $size - 1);
     $items[$random_index] = self::roundWithPrecision($items[$random_index] + $min, $precision_num);
     $sum_item_number = self::roundWithPrecision($sum_item_number + $min, $precision_num);
     $rest = self::roundWithPrecision($number - $sum_item_number, $precision_num);
    } else {
     //剩余的数小于min最小额度，则将这最后的未分配的数随机分配
     $random_index = mt_rand(0, $size - 1);
     $items[$random_index] = self::roundWithPrecision($items[$random_index] + $number - $sum_item_number, $precision_num);
     $sum_item_number = $number;
     $rest = $number - $sum_item_number;
    }
   }
  } else {
   //如果是切割成整数
   $rest = $number - $sum_item_number;
   while ($rest > 0) {
    if ($rest / $min >= 1) {
     $random_index = mt_rand(0, $size - 1);
     $items[$random_index] += $min;
     $sum_item_number += $min;
     $rest = $number - $sum_item_number;
    } else {
     $random_index = mt_rand(0, $size - 1);
     $items[$random_index] += $rest;
     $sum_item_number += $rest;
     $rest = $number - $sum_item_number;
    }
   }
  }
  return $items;
 }
}

　　测试代码：

use Werben\Tools\NumberSlicing;
 
function testIntSlicing2IntOne() {
 $precision = 1; //精确度 eg: 1, 0.1, 0.01, 0.01
 $size = 10;   //切割的份数，the size of the number to slicing
 $min = 3;  //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
 $number = 100;  //要切割的数字，the number
 $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);
 $sum = 0.0;
 $ret_min = $number;
 foreach ($items as $value) {
  $sum += $value;
  if ($ret_min > $value) {
   $ret_min = $value;
  }
 }
 $count = count($items);
 echo "count: $count, sum: $sum, ret_min: $ret_min\n";
 echo "items : ". json_encode($items) ."\n";
}
function testIntSlicing2IntTwo() {
 $precision = 1; //精确度 eg: 1, 0.1, 0.01, 0.01
 $size = 30;   //切割的份数，the size of the number to slicing
 $min = 18666;  //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
 $number = 800000;  //要切割的数字，the number
 $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);
 $sum = 0.0;
 $ret_min = $number;
 foreach ($items as $value) {
  $sum += $value;
  if ($ret_min > $value) {
   $ret_min = $value;
  }
 }
 $count = count($items);
 echo "count: $count, sum: $sum, ret_min: $ret_min\n";
 echo "items : ". json_encode($items) ."\n";
}
function testIntSlicing2FloatOne() {
 $precision = 0.01; //精确度 eg: 1, 0.1, 0.01, 0.01
 $size = 1000;   //切割的份数，the size of the number to slicing
 $min = 0.05;  //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
 $number = 100;  //要切割的数字，the number
 $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);
 $sum = 0.0;
 $ret_min = $number;
 foreach ($items as $key => $value) {
  $sum += $value;
  if ($ret_min > $value) {
   $ret_min = $value;
  }
 }
 $count = count($items);
 echo "count: $count, sum: $sum, ret_min: $ret_min\n";
 echo "items: ". json_encode($items) ."\n";
}
function testIntSlicing2FloatTwo() {
 $precision = 0.00001; //精确度 eg: 1, 0.1, 0.01, 0.01
 $size = 1000;   //切割的份数，the size of the number to slicing
 $min = 0.00005;  //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
 $number = 5;  //要切割的数字，the number
 $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);
 $sum = 0.0;
 $ret_min = $number;
 foreach ($items as $key => $value) {
  $sum += $value;
  if ($ret_min > $value) {
   $ret_min = $value;
  }
 }
 $count = count($items);
 echo "count: $count, sum: $sum, ret_min: $ret_min\n";
 echo "items: ". json_encode($items) ."\n";
}

总结

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