java实现微信抢红包算法

//二倍均值法
public static List<Integer> divideRedPackage(Integer totalAmount,
             Integer totalPeopleNum) {
  List<Integer> amountList = new ArrayList<Integer>();
 
  //为了使用random.nextInt(Integer)方法不得不先把红包金额放大100倍，最后在main函数里面再除以100
  //这样就可以保证每个人抢到的金额都可以精确到小数点后两位
 
  Integer restAmount = totalAmount * 100;
 
  Integer restPeopleNum = totalPeopleNum;
 
  Random random = new Random();
 
  for (int i = 0; i < totalPeopleNum - 1; i++) {
 
   // 随机范围：[1，剩余人均金额的两倍)，左闭右开
 
   int amount = random.nextInt(restAmount / restPeopleNum * 2 - 1) + 1;
   restAmount -= amount;
   restPeopleNum--;
   amountList.add(amount);
  }
  amountList.add(restAmount);
 
  return amountList;
 }

//线段分割法
private static List<Integer> divide(double money, int n) {
  //验证参数合理校验
  //为了使用random.nextInt(Integer)方法不得不先把红包金额放大100倍，最后在main函数里面再除以100
  //这样就可以保证每个人抢到的金额都可以精确到小数点后两位
  int fen = (int) (money * 100);
  if (fen < n || n < 1) {
   System.out.println("红包个数必须大于0，并且最小红包不少于1分");
  }
  List<Integer> boards = new ArrayList<>();
  boards.add(0);
  boards.add(fen);
  //红包个数和板砖个数的关系
  while (boards.size() <= n) {
   int index = new Random().nextInt(fen - 1) + 1;
   if (boards.contains(index)) {
    //保证板子的位置不相同
    continue;
   }
   boards.add(index);
  }
 
  //计算每个红包的金额，将两个板子之间的钱加起来
  Collections.sort(boards);
  List<Integer> list = new ArrayList<>();
  for (int i = 0; i < boards.size() - 1; i++) {
   Integer e = boards.get(i + 1) - boards.get(i);
   list.add(e);
  }
  return list;
 
 }
 public static void main(String[] args) {
//  List<Integer> accountList = divideRedPackage(50, 1000);
  List<Integer> accountList = divide(50, 10);
  BigDecimal count = new BigDecimal(0);
  for (Integer amount : accountList) {
   //将抢到的金额再除以100进行还原
   BigDecimal tmpcount = new BigDecimal(amount).divide(new BigDecimal(100));
   count = count.add(tmpcount);
   System.out.println("抢到金额：" + tmpcount);
 
  }
  System.out.println("total=" + count);
}