看了微信红包的算法实现探讨（基于PHP）一文，我尝试使用C++重现，代码如下：

#include <iostream>
#include <cstdlib>
#include <ctime>int Random(int _max)
{_max = _max > 0 ? _max : 1;static bool begin = false;if (!begin){srand((unsigned)time(nullptr)); //用于保证是随机数begin = true;}return rand() % _max;  //用rand产生随机数并设定范围
}int main()
{using namespace std;double total_money = 10;int total_people = 8;double min_money = 0.01;double *per_money = new double[total_people];for (int i = 0; i < total_people - 1; i++){double safe = (total_money - (total_people - i)*min_money) / (total_people - i);double var_money = min_money + (double)Random((int)safe * 100) / 100;per_money[i] = var_money;total_money -= var_money;}per_money[total_people - 1] = total_money;for (int i = 0; i < total_people; i++){cout << i << ": " << per_money[i] << endl;}delete[] per_money;return 0;
}

程序运行效果不太理想，最后一个红包金钱额数总是5~10倍于其它红包，这是由于C++提供的随机函数是均匀分布的。运行效果：共10元，8个红包，分配为0.49、0.24、0.01、0.31、0.64、1.33、1.2、5.78。

在网上查找到这一篇微信红包算法探讨，对代码重新封装如下，运行效果不错：

random.h

#ifndef MY_RANDOM_H
#define MY_RANDOM_H#include <cstdlib>
#include <ctime>namespace keyven
{int rand(){static bool begin = false;if (!begin){srand((unsigned)time(nullptr)); //用于保证是随机数begin = true;}return std::rand();  //用rand产生随机数并设定范围}
}#endif

money.h

#ifndef MY_MONEY_H
#define MY_MONEY_H#include "random.h"
#include <cmath>
#include <vector>#define TWO_PI 6.2831853071795864769252866namespace danye_me
{double generateGaussianNoise(const double mu, const double sigma){static bool haveSpare = false;static double rand1, rand2;if (haveSpare){haveSpare = false;return (sigma * sqrt(rand1) * sin(rand2)) + mu;}haveSpare = true;rand1 = keyven::rand() / ((double)RAND_MAX);if (rand1 < 1e-100) rand1 = 1e-100;rand1 = -2 * log(rand1);rand2 = (keyven::rand() / ((double)RAND_MAX)) * TWO_PI;return (sigma * sqrt(rand1) * cos(rand2)) + mu;}std::vector<double> generateMoneyVector(const double mon, const int pics){std::vector<double> valueVec;double moneyLeft = mon - pics * 0.01;double mu, sigma;double noiseValue;double TempSum = 0;for (int i = 0; i < pics - 1; i++){mu = moneyLeft / (pics - i);sigma = mu / 2;noiseValue = generateGaussianNoise(mu, sigma);if (noiseValue < 0) noiseValue = 0;if (noiseValue > moneyLeft) noiseValue = moneyLeft;valueVec.push_back((int)((noiseValue + 0.01) * 100) / (double)100);TempSum += (int)((noiseValue + 0.01) * 100) / (double)100;moneyLeft -= noiseValue;}valueVec.push_back(mon - TempSum);return valueVec;}
}#endif

main.cpp

#include "money.h"
#include <iostream>
#include <iomanip>int main()
{double total_money = 10.8;int people = 7;double Test_Sum = 0;std::vector<double> packets = danye_me::generateMoneyVector(total_money, people);for (std::vector<double>::iterator it = packets.begin(); it != packets.end(); it++){std::cout << std::setprecision(2) << std::setiosflags(std::ios::fixed | std::ios::showpoint) << *it << std::endl;Test_Sum += *it;}std::cout << "Sum: " << Test_Sum << std::endl;system("pause");return 0;
}

运行效果：共10.8元，7个红包，分配为0.87、1.53、1.90、1.92、2.25、0.79、1.54。

有兴趣可以再看看这篇：微信红包的架构设计简介。

Reference

微信红包的算法实现探讨（基于PHP）

微信红包算法探讨

微信红包的架构设计简介